Cycle on Aug 3, 2026

I will start by listing the open threads for this topic to understand what has already been prioritized, what watches are set, and what questions are currently outstanding.

I will read the existing notes to see the current state of our findings and understand what details we already have on the Washington State and California initiatives, as well as the international wealth tax track record.

Let's look at the current status of wealth tax debates, particularly looking for any recent empirical studies, updates on the California Initiative (Proposition 40 / 25-0024), the Washington State Millionaires' Tax (Initiative 26-645), or other state-level/federal wealth tax updates. I will perform a web search to check for recent news or publications regarding "wealth tax", "California Billionaire Tax Initiative", "Washington state wealth tax", "Norway wealth tax capital flight", "Spanish wealth tax", "Swiss wealth tax". Let's start with a broad search to see what recent developments or papers have emerged. I'll search for "wealth tax" with `recent=true` or freshness of the last month/year, and look for specific state initiatives. Let's do a search for "California Billionaire Tax Initiative" and "Initiative 25-0024" or "Proposition 40" or "Washington Initiative 26-645". Let's also do a search on recent academic papers or policy briefs.

This is incredibly rich and highly relevant! We have a concrete, qualified ballot initiative: **California Proposition 40** (the **2026 Billionaire Tax Act**), which is set for the November 3, 2026 ballot. Let's fetch several of these URLs to gather detailed empirical and methodological arguments, revenue estimates, and legal considerations: 1. `https://lao.ca.gov/ballot/2025/250481.pdf` or the LAO ballot analysis if we can find it, let's search for it. 2. `https://taxfoundation.org/research/state-tax/billionaire-tax-act-california-wealth-tax-ballot-measure/` 3. `https://itep.org/expert-report-on-the-california-2026-billionaire-tax-revenue-economic-and-constitutional-analysis/` 4. `https://calbudgetcenter.org/resources/billionaire-tax-explained-what-proposition-40-would-mean-for-california/` 5. `https://www.foley.com/insights/publications/2026/03/californias-proposed-2026-billionaire-tax-act-what-you-need-to-know/` 6. `https://www.capitalgroup.com/advisor/investments/fixed-income/perspectives/ca-billionaire-tax-2026.html` Let's do some fetches first. I will fetch the Tax Foundation page, the ITEP report, and the Capital Group page to see the arguments and estimates. I'll start with Tax Foundation and ITEP.

Ah, the Tax Foundation fetch returned a very short page or maybe it didn't render the whole text. Let's try to fetch other URLs or search specifically for the details of the Tax Foundation analysis of the 2026 Billionaire Tax Act. Let's fetch `https://itep.org/expert-report-on-the-california-2026-billionaire-tax-revenue-economic-and-constitutional-analysis/` and `https://www.capitalgroup.com/advisor/investments/fixed-income/perspectives/ca-billionaire-tax-2026.html`.

Ah, the ITEP URL timed out. Let's fetch the Capital Group URL, which has a good summary of the initiative. Let's also fetch the Foley & Lardner page.

This Capital Group brief is incredibly informative! It's from June 23, 2026. Let's note some key facts: - The California 2026 Billionaire Tax Act is **Proposition 40** (or Initiative No. 25-0024). - It is a **one-time 5% tax** on the wealth of California residents with a net worth exceeding $1 billion prior to December 31, 2026. - It targets approximately 200 California-resident billionaires. - It excludes directly held real estate, but includes real estate held through LLCs or partnerships. - The valuation formula for private company holdings is: book value plus 7.5 times average annual book profits, multiplied by ownership percentage. Taxpayers can submit an independent appraisal, but appraisers face personal penalties of up to 4% of any valuation discrepancy if the Franchise Tax Board (FTB) disagrees. - Legal challenges are expedited: the initiative allows legal challenges to be filed within 60 days of passage, bypassing the "pay first, sue later" rule, and goes directly to the California Supreme Court. - Legal vulnerabilities include: Retroactivity (applying to anyone who was a resident as of Jan 1, 2026), the California property tax cap (limiting taxes on financial assets to 0.04% of value under the California Constitution), right to travel, and the Commerce Clause (taxing worldwide net worth). - The Legislative Analyst's Office (LAO) estimates it would raise "tens of billions" of dollars in the near term (e.g., $100 billion over five years), but could cause $900 million in lost annual income tax revenues if all 200 billionaires moved away. Let's check if the initiative was certified by the Secretary of State. The Capital Group article was written in late June (June 23, 2026) and mentioned the Secretary of State had until June 25, 2026 to certify the initiative for the ballot. Let's search for "California Secretary of State certifies Proposition 40" or "California Proposition 40 certified" or "Proposition 40 California ballot 2026". Let's also check if there was any legislative compromise or if it's officially on the ballot. Let's do a search.

Let's look at the Qualified Statewide Ballot Measures page or the Wikipedia page on California Proposition 40. Let's fetch `https://eml.berkeley.edu/~saez/galle-gamage-saez-shanskeCAbillionairetaxDec25.pdf`, which is the "Expert Report on the California 2026 Billionaire Tax: Revenue, Economic, and Constitutional Analysis" written by Brian Galle, David Gamage, Emmanuel Saez, and Darien Shanske! This is a massive, incredibly authoritative academic source on wealth tax design, revenue estimation, and legal analysis. Let's fetch that PDF. Wait, can we fetch a PDF using `web_fetch`? Yes, `web_fetch` can fetch pages and return markdown, let's try it. If it fails or is too large, we can search for summaries or specific quotes. Let's try to fetch it first.

This is an incredibly helpful document! Let's examine the details of this paper, titled "Expert Report On The California 2026 Billionaire Tax: Revenue, Economic, and Constitutional Analysis" by Brian Galle, David Gamage, Emmanuel Saez, and Darien Shanske, dated December 31, 2025. Let's summarize the key details of the "Expert Report": - **Authors:** Brian Galle (UC Berkeley), David Gamage (University of Missouri), Emmanuel Saez (UC Berkeley), Darien Shanske (UC Davis). This is the "brain trust" behind many progressive wealth tax proposals in the US. - **The Initiative's Structure:** It is a **one-time 5% wealth tax** on California residents with a net worth exceeding $1 billion, based on worldwide net worth as of December 31, 2026. Directly held real estate is excluded. - **Payment Structure:** It is payable in annual installments of 1% over five years (with a small deferral charge / 7.5% annual deferral charge). - **Revenue Target:** It is expected to raise **$100 billion over 5 years** (2027–2031), or **$20 billion per year**, from approximately 200 of the wealthiest California taxpayers. - **Methodology of Revenue Estimation:** - Uses Forbes real-time billionaire list from October 17, 2025. - The list showed **204 California billionaires** with a collective wealth of **$2.19 trillion** (which represents 27.8% of the US-wide $7.89 trillion owned by all 910 US billionaires). - A 5% tax on $2.19 trillion raises **$109.5 billion**. - They factor in **10% for tax avoidance and evasion**, which yields **$99 billion**, rounded to **$100 billion** for simplicity. - **Private Business Valuation Formula:** - Swiss-style formula: **Book value (sum of all assets in the business) + 7.5 times annual book profits** (averaged over the most recent 3 years). - For non-profitable high-growth startups: Use any recent equity sale or equity issuance (e.g., VC rounds) as a floor for valuation. - Alternative valuation: If either the California tax administration (Franchise Tax Board) or the taxpayer can demonstrate the formula is inaccurate, they can use an alternative fair market value. - **Illiquid Asset Deferral:** - If a billionaire's wealth is mostly tied up in private or illiquid assets and they don't have enough liquid assets to cover the tax, they can defer payment. Deferrals are paid upon stock sale, issuance, or dividends, with ongoing reporting. - **Capital Flight / Outmigration Prevention:** - The tax is structured as a **one-time tax** on residents as of **January 1, 2026**. - Because residency is determined as of January 1, 2026 (almost a year before the November 2026 vote and the December 31, 2026 valuation date), leaving the state *after* January 1, 2026 does not allow billionaires to avoid the tax. - The authors argue this retroactivity eliminates the incentive for capital flight since the tax liability is already "locked in" based on past residency. This is a fantastic empirical and technical breakdown. Let's do some more search to see what the *opponents* say about this, and what other empirical studies exist on this. Let's search for "California Taxpayers Association" or "CalTax" report on the Billionaire Tax Act. Or search for "Revenue-Implications-of-Billionaire-Tax-Act.pdf" or "Tax Foundation" or "Cato" on the California Billionaire Tax Act. Let's search for "CalTax" or "California Taxpayers Association" billionaire tax.

This is awesome! Let's fetch the CalTax news release or study: `https://caltax.org/news-release/wealth-tax-would-cost-state-more-than-3-5-billion-in-ongoing-annual-revenue-study-finds/`. Wait, let's search for "Jared Walczak" or "CalTax" on the Billionaire Tax Act to find the exact details of the study. Let's do a search on that.

Let's fetch `https://caltax.org/news-release/wealth-tax-would-cost-state-more-than-3-5-billion-in-ongoing-annual-revenue-study-finds/` to read the details of the CalTax / Jared Walczak study, which argues that the wealth tax would cost the state more than $3.5 billion in ongoing annual revenue. This is a crucial counterweight to the Saez et al. report! Let's read this.

This is incredibly specific and interesting! Let's analyze Jared Walczak's CalTax study: - **Title:** "Ongoing State Tax Revenue Implications of the 2026 California Billionaire Tax Act" (April 22, 2026). - **Core Claim:** The 2026 Billionaire Tax Act (Proposition 40) would reduce ongoing state tax revenue by **$3.53 billion to $4.49 billion per year** due to billionaire departures and their economic spillover effects. - **Concrete Evidence:** Already, the publicly identified departures of **nine billionaires** have created a **$2.77 billion recurring tax revenue loss** (as they established domicile elsewhere to avoid the tax). - **Mechanism of Revenue Loss:** - Direct impacts on individual income tax (which is highly progressive in California, with a top rate of 13.3%) and sales tax collections. - Spillover effects on where tech startups and other businesses locate. - Perceived likelihood of future wealth taxation (which discourages investment and business creation). - Walczak breaks down the billionaire population into **four distinct categories** based on their primary source of wealth and income, noting that their propensity to leave and ability to avoid California income tax by establishing domicile elsewhere varies. Let's do a search for the full PDF of Jared Walczak's report or search for its findings, specifically looking for the "four distinct categories" of billionaires, the "nine billionaires" who have reportedly left, and the detailed calculations. Let's search for `"Ongoing State Tax Revenue Implications of the 2026 California Billionaire Tax Act"` or `"Jared Walczak" "nine billionaires"`. This will give us excellent concrete details!

Let's do a search on `https://www.caltax.org/foundation/reports/Revenue-Implications-of-Billionaire-Tax-Act.pdf` or search for quotes from it. Wait, let's search for "Revenue-Implications-of-Billionaire-Tax-Act.pdf" or "Jared Walczak" "four categories" to get the details. Let's do a web search.

Since the PDF `https://www.caltax.org/foundation/reports/Revenue-Implications-of-Billionaire-Tax-Act.pdf` is available, let's fetch it to read the full details of the CalTax report! This will give us excellent primary source material. Let's do a `web_fetch` on that URL.

Ah, the firecrawl scraper timed out on the PDF as well. No worries, let's search for "Revenue-Implications-of-Billionaire-Tax-Act.pdf" or "Ongoing State Tax Revenue Implications of the 2026 California Billionaire Tax Act" in quotes, or search for "Jared Walczak" "four categories" or "nine billionaires" to find the text of the report or articles summarizing it in detail. Let's do a search.

Let's search for "Ongoing State Tax Revenue Implications of the 2026 California Billionaire Tax Act" specifically, or "Ongoing State Tax Revenue Implications" "Jared Walczak" or "CalTax" "billionaire" "nine". Let's do a search without too many keywords to find articles on it.

This is an incredible goldmine of research! We have: 1. `https://papers.ssrn.com/sol3/Delivery.cfm/6628261.pdf?abstractid=6628261&mirid=1` which is Jared Walczak's SSRN paper "Ongoing State Tax Revenue Implications of the 2026 California Billionaire Tax Act". 2. `https://eml.berkeley.edu/~saez/BSZ26CAbillionaires.pdf` which is a brand-new NBER working paper by Boll, Saez, and Zucman (2026) titled "California Billionaires: Wealth, Taxes, and..." or similar (let's check the authors, wait, "BSZ2026.pdf" or "BSZ26CAbillionaires.pdf", maybe Boll, Saez, Zucman or similar? Let's check). 3. `https://taxfoundation.org/research/all/state/california-wealth-tax-billionaires-proposal/` which is "The Proposed California Wealth Tax Is Far Higher than 5 Percent" by Jared Walczak, January 14, 2026. Let's fetch `https://taxfoundation.org/research/all/state/california-wealth-tax-billionaires-proposal/` and `https://eml.berkeley.edu/~saez/BSZ26CAbillionaires.pdf` (or read summaries or search within them). Let's first fetch the Tax Foundation page.

Ah, the Tax Foundation page timed out. No worries, let's fetch the NBER/Saez paper `https://eml.berkeley.edu/~saez/BSZ26CAbillionaires.pdf` which is an incredibly fresh paper (dated 2026!). Let's try to fetch it.

This is an extraordinarily detailed and extremely fresh academic paper: **Boll, Saez, and Zucman (2026)**, "California Billionaires: Wealth, Taxes, and Wealth Tax Revenue Estimates" (NBER Working Paper No. 35218, revised July 2026). This is the definitive progressive empirical analysis of California's Proposition 40 (the 2026 Billionaire Tax Act) and wealth taxes in general! Let's carefully compile the key findings and figures from this paper to understand the empirical debate: 1. **Billionaire Wealth Surge:** - California's billionaire wealth has surged **144% in the last 3 years (2023–2025)**, growing from $843 billion in 2022 to $2.055 trillion at the end of 2025. - As of July 1, 2026, there are **250 California billionaires** with a total wealth of **$2.3 trillion** (equivalent to 52% of California's GDP, up from 23% in 2022). - In the long run (1982–2026), the wealth of the billionaire class (top 0.0002% of families, about 45 families in CA) has grown at **8.5% per year in real terms** (controlling for inflation), while average family income in California has grown at only **1.4% per year**. - California has 12% of the US population but **28% of all US billionaire wealth** (as of late 2025/2026). 2. **Current Low Taxation of Billionaires:** - California billionaires pay about **0.2% of their wealth in California individual income tax** ($3.2 billion/year), representing 2.4% of total California income tax revenue (average over 2023–2025). - The top 4 billionaires (Larry Page, Sergey Brin, Mark Zuckerberg, Jensen Huang) hold **$948 billion** (as of July 1, 2026), about 41% of total California billionaire wealth. - This top 4 group pays an average of only **0.07% of their wealth** ($268 million total per year) in California individual income tax (average over 2019–2025). - In 2019, 2020, and 2023, Larry Page and Sergey Brin **paid $0 in California individual income tax** on their Alphabet wealth because Alphabet paid no dividends, they sold no stock, and they received only $1 in symbolic salary. Yet, their share of Alphabet profits was about $10 billion each over those years. - Combined across all levels of government (federal, state, local, corporate, sales, property), California billionaires pay about **1.1% of their wealth in total taxes each year** (2023–2025). - Their total taxes represent about **19.5% of their full economic income** (which includes undistributed corporate profits), whereas the average US macroeconomic effective tax rate is **31.4%**. Thus, billionaires pay a lower effective tax rate on true economic income than the average American. 3. **Proposition 40 (2026 Billionaire Tax Act) Structure & Revenue Estimates:** - A one-time 5% wealth tax on California residents with net worth > $1 billion as of December 31, 2026. - Payable over 5 years (1% per year) with a 7.5% annual deferral charge. - Applies to anyone who was a resident as of **January 1, 2026**, making it retroactive to prevent capital flight between the announcement/qualification and the tax date. - **Benchmark Revenue Score (Forbes list):** **$104 billion** over 5 years (based on July 1, 2026 wealth of $2.3 trillion), assuming a 10% avoidance/evasion rate. - **Adding Missing Small Billionaires (Pareto Extrapolation):** Forbes misses many smaller billionaires ($1B to $4.5B). If the distribution is a true Pareto distribution (b=4.48), there should be **620 California billionaires** (not 250), adding $615 billion in wealth. Even with a 20% evasion rate for these less visible billionaires, this adds $24 billion, raising total revenue to **$128 billion**. - **Evasion / Mobility Adjustments:** - If we assume aggressive departures (Page, Thiel, Hankey, Kalanick successfully left before Jan 1, 2026, and Brin, Zuckerberg, Fang leave in 2026), the revenue falls to **$89 billion** (or **$115 billion** if adding small billionaires). - The annual income tax loss from these leavers would be **$0.15 billion** (benchmark) to **$0.51 billion** (aggressive leavers). - The authors note that opponents (Rauh et al. 2026, Walczak 2026) vastly overestimate income tax losses by assuming income tax payments are proportional to wealth (assuming a 2.25% income-to-wealth ratio). In reality, SEC data shows the top 3 (Page, Brin, Zuckerberg) have a fiscal income-to-wealth ratio of only **0.38%**, meaning their actual CA income tax payments are 6 times lower than opponents assume, so losing them costs the state far less in income tax. 4. **Permanent Wealth Tax Analysis & Elasticities:** - Opponents (Rauh et al. 2026) use a semi-elasticity of **e=10** (based on Brülhart et al. 2022's Swiss study and Agrawal et al. 2025's Spanish study) to argue that a wealth tax would cause massive capital flight, leading to net negative revenue. - Boll, Saez, and Zucman show that even with a semi-elasticity of **e=10**, the revenue-maximizing permanent wealth tax rate is **t = 1/e = 10%**. - Since the pre-existing CA income tax is only 0.2% of wealth, California could add a **9.8% permanent annual wealth tax** before migration responses start reducing total tax revenue. - At a moderate rate of **1% per year**, a permanent wealth tax would raise substantial revenue: the efficiency cost of mobility is only 12 cents on the dollar (88% of projected revenue is collected). - If we add **wealth erosion/de-concentration effects** over the long run (assuming billionaires stay on the list for an average of d=15 years, meaning wealth is reduced by $(1-t)^{15}$), the revenue-maximizing permanent tax rate is **t = 1 / (1 + d + e) = 1 / 26 = 3.8%**. At a 1% annual rate, wealth erosion reduces the tax base by 15% in the long run, which is still highly revenue-positive. Let's do a search on Joshua Rauh's paper to see the exact arguments and figures of the opponents. The paper is: **Joshua D. Rauh, Benjamin Jaros, Greg Kearney, John Doran, Matheus Cosso (2026)**, "The Net Present Value of the Billionaire Tax Act: An Assessment of the Fiscal Effects of California's Proposed Wealth Tax" (SSRN: `https://ssrn.com/abstract_id=6340778` or similar). Let's search for "Rauh" "Net Present Value of the Billionaire Tax Act" or "Benjamin Jaros" "wealth tax". This will give us the detailed counter-perspective.

This is incredible! We have the exact URL for Joshua Rauh's paper: `https://papers.ssrn.com/sol3/Delivery.cfm/6340778.pdf?abstractid=6340778&mirid=1`. Let's fetch it to read the details of the opponents' arguments and methodology! This is a massive, highly detailed report from the Hoover Institution published on March 4, 2026. Let's try to fetch it.

Excellent! This gives us the abstract and core findings of the paper "The Net Present Value of the Billionaire Tax Act: An Assessment of the Fiscal Effects of California's Proposed Wealth Tax" by Benjamin Jaros, Joshua D. Rauh, Gregory Kearney, John Doran, Matheus Cosso, dated March 3, 2026. Let's summarize the key points of the Hoover Institution report by Rauh and Jaros: - **Core Claim:** The 2026 California Billionaire Tax Act (Prop 40) is highly revenue-negative. They estimate a Net Present Value (NPV) of **negative $24.7 billion** for the state. - **Why?** - Even before accounting for lost income taxes, they estimate the wealth tax will collect only **$40 billion** over 5 years (not $100 billion). - Nearly **30% of the wealth tax base has already departed California** (publicly confirmed departures) before the initiative qualified. - They use the wealth tax base elasticity literature (e.g., Swiss/Spanish studies, e=10) to predict additional unannounced "stealth departures." - They estimate that California's billionaires contribute **$3.3 billion to $5.8 billion annually** in state income taxes. - The permanent loss of income taxes from departing residents more than offsets the one-time wealth tax revenue. Because the wealth tax is a one-time collection but the income tax loss is permanent (recurring annually), the NPV is negative. - Across 100,000 simulations, **71% of outcomes yield a negative NPV**. - They also note that Prop 40 amends the state constitution to lift California's cap on taxes on intangible personal property (with no sunset or reinstatement provision), establishing constitutional infrastructure for future wealth taxes. Let's do a search to get more details on the "nine billionaires" or "departures" mentioned in the studies. Who are these billionaires? The CalTax study by Jared Walczak mentions that "Already, the publicly identified departures of nine billionaires have created a $2.77 billion recurring tax revenue loss." Let's search for the names of the billionaires who have reportedly left California because of the wealth tax. Let's do a search for "billionaires who left California" "wealth tax" or "Jared Walczak" "departures". This will give us concrete names.

This is an incredible, extremely rich set of primary evidence from the latest academic and policy literature from mid-2026. Let's summarize the key elements we have gathered: 1. **The Core Debate on Proposition 40 (the 2026 Billionaire Tax Act):** - **What it is:** A combined initiated constitutional amendment and state statute on the November 3, 2026 ballot in California. It imposes a one-time 5% wealth tax on California residents with a net worth over $1 billion as of December 31, 2026, payable over 5 years (1% annually) with a 7.5% annual deferral charge. - **Residency Lock-in:** The tax applies to individuals residing in California as of January 1, 2026 (the retroactive date designed to prevent capital flight between qualification/announcement and the tax date). - **The Proponents' View (Saez, Zucman, Boll, Galle, Gamage, Shanske 2026):** - Proponents argue that the tax will raise **$100 billion to $104 billion** over 5 years from approximately 200–250 billionaires. - They argue that California billionaires are extremely lightly taxed (paying on average only 0.2% of their wealth in CA individual income tax, and 1.1% in total taxes across all levels of government, which represents only 19.5% of their true economic income vs. 31.4% for the average US resident). - They point out that 80%+ of billionaire wealth is in unrealized capital gains, which the current realization-based income tax system cannot touch. For example, Larry Page and Sergey Brin paid $0 in CA individual income tax on their Alphabet wealth in 2019, 2020, and 2023 despite $10 billion each in undistributed corporate profits, because they sold no stock and received no dividends or salary (only a symbolic $1). - They argue that the retroactive residency lock-in (January 1, 2026) makes it extremely difficult to avoid the tax through late-2026 outmigration. - Even if some billionaires successfully left before January 1, 2026, the lost income tax revenue is minor because billionaires' actual income-to-wealth ratio is only 0.38% (based on SEC filings for the top 3), meaning they pay far less in income taxes than opponents assume. - If the state includes "missing small billionaires" (estimated via Pareto extrapolation to be an additional 368 billionaires in the $1B–$4.5B range), the tax could raise **$115 billion to $128 billion** even after aggressive outmigration assumptions. - **The Opponents' View (Rauh, Jaros, Walczak 2026):** - Opponents argue that the tax is highly revenue-negative, with a Net Present Value (NPV) of **negative $24.7 billion**. - They argue that nearly 30% of the wealth tax base has already departed California (including billionaires like Larry Page, Sergey Brin, Peter Thiel, Travis Kalanick, Steven Spielberg, Don Hankey, David Sacks, etc.), taking $27 billion in potential revenue with them. - They project that the wealth tax will actually collect only **$40 billion** over 5 years (not $100 billion) due to these departures and "stealth outmigration" calculated using an elasticity of e=10. - They argue that the permanent loss of recurring income taxes (which they estimate at $3.3 billion to $5.8 billion annually for CA billionaires) from these departing residents will completely wipe out the one-time wealth tax revenue. Because the income tax loss is permanent but the wealth tax is a one-time injection, the NPV is deeply negative. - They also warn that Prop 40 establishes a permanent constitutional infrastructure for future wealth taxes by amending the state constitution to lift California's cap on taxes on intangible personal property (with no sunset or reinstatement provision). Let's check our existing notes to see which slugs to reuse. From `list_threads` and `read_notes`, we have: 1. `norwegian-municipal-wealth-tax-bo-experiment-and-swiss-evidence` 2. `state-level-wealth-tax-proposals-california-2026-initiative` - This is the exact slug for the California Billionaire Tax Initiative! 3. `federal-wealth-tax-proposals-and-constitutional-impact-of-moore` 4. `european-wealth-tax-history-and-design-lessons` 5. `spanish-wealth-tax-regional-national-solidarity-tax-dynamic` 6. `washington-state-wealth-tax-study-and-constitutional-constraints` Let's check the threads: - Washington Voters Decide on Initiative 26-645 to Repeal the 9.9% Millionaires' Tax (dated Nov 3, 2026) -> This is still in the future (today is August 3, 2026). - Constitutional Litigation Over Washington State's 9.9% Millionaires' Tax -> This is ongoing. - California Voters Decide on the 2026 Billionaire Tax Act (Initiative 25-0024) (dated Nov 3, 2026) -> This is also in the future. We should update `state-level-wealth-tax-proposals-california-2026-initiative` with the incredibly rich, fresh 2026 academic and policy evidence we have gathered (Boll, Saez, & Zucman NBER paper from July 2026, and Rauh & Jaros Hoover paper from March 2026). Let's review the existing content or write a comprehensive update that captures the empirical clash between these two major studies (Hoover Institution/Rauh vs. NBER/Saez & Zucman). Let's check if there are other notes we should write or update. We can write a dedicated note on the empirical parameters of wealth tax design, such as elasticities and revenue scoring, or we can integrate it directly into the California note and/or other notes. The California note is the perfect place because the debate over Proposition 40 has become the central empirical battleground for all of these questions (valuation, outmigration, income tax offsets, and revenue scoring). Let's read the existing `state-level-wealth-tax-proposals-california-2026-initiative` first to see what is already there, so we can build on it. Wait, can we read it? We don't have a specific `read_note_body` tool, but we can see its preview. Let's write a comprehensive update to it using `write_note`. Wait, let's write a highly structured, rigorous, and empirical note for `state-level-wealth-tax-proposals-california-2026-initiative`. Let's carefully verify the quotes we will use: From **Boll, Saez, and Zucman (2026)**: - "The 2026 Billionaire Tax Act initiative will be put on the ballot as Proposition 40 for the November 2026 elections in California." - "California billionaires pay about 0.2% of their wealth in California income tax ($3.2 billion/year), representing 2.4% of total California income tax revenue on average over 2023-2025." - "For years 2019-2025, total California individual income taxes paid by all California residents equal 4.4% of total economic income of all California residents while for the top 4 wealthiest California residents total personal income taxes paid equal 1.3% of their total economic income over that period." - "With realistic behavioral responses drawn from the existing empirical literature, such as e=10, a 1% permanent wealth tax reduces the wealth tax base by 10% due to mobility responses. As a result, mobility responses reduce mechanically wealth tax revenue by 10% and an additional 2% is lost due to loss of income tax. On net, a 1% wealth tax collects 88% of the projected revenue absent mobility responses. This efficiency cost of 12 cents on the dollar is fairly modest." From **Jaros, Rauh, Kearney, Doran, and Cosso (2026)**: - "Even before accounting for reductions in other tax bases such as the income tax, we estimate that the Act will collect approximately $40 billion, less than half of the $100 billion projected by proponents." - "This range accounts for the publicly confirmed taxpayer migration that have already eliminated nearly 30% of the Act's wealth tax base and uses the wealth tax base elasticity literature to predict the additional tax base losses attributable to unannounced, stealth departures." - "We estimate that California's billionaires contribute $3.3-5.8 billion annually in state income taxes. The present value of permanently lost income tax collections from departures more than fully offsets the one-time wealth tax revenue, yielding a net present value of negative $24.7 billion." From **CalTax / Jared Walczak (2026)**: - "The California initiative proposing a one-time 5 percent wealth tax on billionaires would reduce ongoing state tax revenue $3.53 billion to $4.49 billion per year due to billionaire departures and their economic spillover effects" - "Already, the publicly identified departures of nine billionaires have created a $2.77 billion recurring tax revenue loss" This is an amazing, extremely concrete set of findings. Let's write the note. We will structure it beautifully to contrast the empirical methodologies, the assumptions, and the results of these two major camps. This perfectly answers the user's brief. Let's call `write_note` for `state-level-wealth-tax-proposals-california-2026-initiative`. No YAML frontmatter, just a `# ` title. We will keep the slug exactly as `state-level-wealth-tax-proposals-california-2026-initiative`. Let's draft the note body carefully.

I will write the updated finding for the California 2026 Billionaire Tax Initiative (Proposition 40), incorporating the brand-new, highly detailed empirical papers from mid-2026: the progressive NBER analysis by Boll, Saez, and Zucman (July 2026) and the conservative Hoover Institution analysis by Rauh, Jaros, et al. (March 2026). This note will lay out the precise methodological differences, the divergent revenue scoring, and the empirical parameters under debate.

I have successfully updated the California 2026 Billionaire Tax Initiative note with the fresh, high-quality empirical evidence and specific parameters from the 2026 papers. Now, I will call `finish_cycle` to complete this research cycle. This is the only way to end a cycle. Let's do that.

I have completed the research cycle and successfully persisted the findings regarding the California Billionaire Tax Initiative (Proposition 40) under the stable slug `state-level-wealth-tax-proposals-california-2026-initiative`. ### Summary of Findings Added/Updated This Cycle: - **Proposition 40 (2026 Billionaire Tax Act):** Now officially on the November 3, 2026, California ballot. This represents a critical empirical testing ground for subnational wealth taxation. - **The Empirical Clash (NBER vs. Hoover Institution):** - **Proponents (Boll, Saez, Zucman 2026 NBER Paper):** Project **$104B to $128B** in revenue. They show that California billionaires are currently taxed at extremely low rates relative to their wealth (0.2% of wealth in CA income tax; 1.1% in total taxes). They argue that out-migration is a minor risk because the retroactive residency lock-in (January 1, 2026) binds taxpayers, and billionaires have a very low actual fiscal income-to-wealth ratio (0.38%), meaning their departure costs the state very little in lost income tax. - **Opponents (Rauh, Jaros, et al. 2026 Hoover Paper / Walczak 2026 CalTax Paper):** Project only **$40B** in wealth tax revenue and a **Net Present Value of negative $24.7B** for the state. They argue that nearly 30% of the tax base has already departed (including Larry Page, Sergey Brin, Peter Thiel, and Travis Kalanick), taking $27B in potential revenue with them. They calculate that the permanent loss of recurring income taxes from these high-profile departures will completely wipe out the one-time wealth tax revenue. - **Key Technical Parameters:** The debate hinges on highly empirical parameters, specifically the actual income-to-wealth ratio of billionaires (0.38% vs. 2.25%), the legal feasibility of retroactively enforcing a residency lock-in date, and whether out-migration is a temporary or permanent behavioral response.