BSZ analysis of California Proposition 40: Overview · Open Output (here) · Open Analysis: Report and Slides · Open Materials Also in this project: Comparison overview · JR analysis overview

How much would the one-time billionaire tax raise, net?

Boll, Saez and Zucman (BSZ, 2026) estimate about $100 billion of wealth tax ($104 billion in their Table 5). Add the income tax the tax changes and the total is this site's main estimate. Most of its inputs are guesswork. Move them and the estimate updates: every setting is precomputed by the pipeline that reproduces the authors' workbook.

Defined as the wealth tax, plus the extra income tax from assets sold to pay it, minus the income tax lost to billionaires who leave, counted over 5 years in today's dollars (present value at 3% a year).

The inputs

the value the authors use

Levels other than the authors' are this OPA's, chosen to bracket the authors' value; the two yes/no switches instead turn on the authors' own Table 5 scenarios (rows 2 to 4). The explorer holds every combination. Origins follow the OPA taxonomy: data (settled by observable facts), research (a published estimate), guesswork (asserted without data or a study behind it), scenario (a choice of which world is estimated).

Outcomes

¹ The main estimate is not the authors' choice: BSZ's headline is the wealth tax alone, about $100 billion in the abstract and $104 billion in Table 5 (reproduced here as ). This OPA uses the total because it compares more directly with the JR analysis's net present value; the comparison overview puts both on one definition.

Jump to a scenario

Every outcome, for this setting and the four Table 5 scenarios

Nominal dollars, 1 July 2026 Forbes wealth. The orange column is the main estimate.
Outcome	This setting

Notes and data

Horizon. The income tax lost to leavers recurs every year they stay away. BSZ argue about 5 years (PDF p.27). The main estimate counts 5 years at 3% a year, the middle of the JR analysis's 1.5% to 4.5% range (BSZ give no rate). The JR analysis counts it forever: see the comparison overview.

Two departures from the workbook. (1) Its income tax loss is a literal 5% (Tab5!H6); the explorer reads it as avoidance times the share leaving, identical at the authors' values. (2) Table 5 deducts the $1B to $1.1B phase-in in row 2 but not row 4 (Tab5!F9). The explorer copies this, so with both switches on the estimate is higher than a consistent treatment.

Data. grid.csv (every setting), inputs.csv (every input and its origin), grid.js (what this page reads). The pipeline writes all three; a test fails if grid.js differs from its output.