An individual taxed at an average 25% earning 5.7% on Treasury bills over 47 years would have had zero real income after taxes and inflation.

Factual/arithmetic claim judged as of the 2011 letter (February 2012). True: Treasury bill returns over the 47 years to 2011 averaged about 5.7% a year, and inflation over that period averaged about 4.3%, so 5.7% × (1 − 0.25) ≈ 4.3% equals inflation and real after-tax income is about zero. Mostly true: the numbers are slightly off (T-bill average within about 0.3 pp of 5.7%, or inflation within about 0.3 pp of the after-tax yield), so real income is near zero. Mixed: the arithmetic holds but the inflation or T-bill figure is clearly different, leaving a real result noticeably above or below zero. Mostly false: the sources show the after-tax real return was clearly positive or negative (by more than about 0.7 pp a year). False: the 5.7% T-bill average or the inflation figure is wrong outright, making the zero-real-income result false.

Set before the research began.

1. E1 Warren Buffett's 2011 Shareholder Letter Midgard Finance (reproduction of Berkshire Hathaway 2011 letter) · 25 February 2012 Own record

   “During the same 47-year period, continuous rolling of U.S. Treasury bills produced 5.7% annually.”

2. E2 Annual Returns on Stock, T.Bonds and T.Bills: 1928 - Current Aswath Damodaran, NYU Stern School of Business · 5 January 2019

   “| 2011 | 2.10% | 0.03% | 16.04% | $ 166,871.56 | $ 1,970.44 | $ 6,726.52 | 2.07% | -13.94% |”

3. E3 Consumer Price Index, 1913- | Federal Reserve Bank of Minneapolis Federal Reserve Bank of Minneapolis

   “| 2011 | 224.9 | 3.2% |”

4. E4 Warren Buffett's 2011 Shareholder Letter Midgard Finance (reproduction of Berkshire Hathaway 2011 letter) · 25 February 2012 Own record

   “February 25, 2012 Warren E. Buffett Chairman of the Board”

5. E5 Table Data - 3-Month Treasury Bill Secondary Market Rate, Discount Basis Federal Reserve Bank of St. Louis (FRED), data from Board of Governors of the Federal Reserve System

   “| 1965-01-01 | 3.81 |”

6. E6 Table Data - 3-Month Treasury Bill Secondary Market Rate, Discount Basis Federal Reserve Bank of St. Louis (FRED), data from Board of Governors of the Federal Reserve System

   “| 2011-06-01 | 0.04 |”

7. E7 Historical Returns on Stocks, Bonds and Bills: 1928-2024 NYU Stern (Aswath Damodaran) · 5 January 2026

   “| 2011 | 2.10% | -14.04% | 0.05% | 16.04% | 12.26% | -3.89% | 12.02% | $ 166,871.56 | $ 1,837,807.31 | $ 2,062.50 | $ 6,726.52 | $ 30,038.58 | $ 2,315.25 | $ 7,628.39 |”

8. E8 Historical Returns on Stocks, Bonds and Bills: 1928-2024 NYU Stern (Aswath Damodaran) · 5 January 2026

   “| 1964 | 16.42% | 23.25% | 3.55% | 3.73% | 5.16% | 1.26% | 0.03% | $ 2,661.02 | $ 10,265.22 | $ 173.20 | $ 272.53 | $ 583.85 | $ 273.78 | $ 170.06 |”

9. E9 2011 letter (.pdf) Berkshire Hathaway Inc. · 25 February 2012 Own record

   “During the same 47-year period, continuous rolling of U.S. Treasury bills produced 5.7% annually.”

The 5.7% annual T-bill figure comes only from Buffett's own 2011 letter (E1, E11), so it is the subject's own assertion and not an independent check. The independent items do not establish the 47-year averages. E7 and E8 give single monthly T-bill rates. E3 gives only the 2011 CPI level, with no 1964 baseline, so average inflation cannot be computed. The Damodaran rows (E2, E9, E10) are table rows without column labels, so the quotes do not say which return or cumulative value each number measures. The evidence therefore cannot confirm that a 5.7% return taxed at 25% (about 4.3% after tax) matched average inflation over the period.