Darby's Widgets
Small, interactive tools for exploring data.
S&P 500 Regression Trend Lines
Monthly S&P 500 closes from 1928 through December 2025, with linear, exponential, and log-quadratic trend lines fit from every start month. Compare fits and implied annual growth rates.
US Deficit Regression Trend Lines
Federal deficits, spending and revenue from 1901 to 2025, fit with the same trend-line math as the S&P 500, plus interest as a share of GDP, tests of whether borrowing and the market move together, and a projection of whether the interest burden is sustainable.