Alpha

Alpha measures how much a trade or portfolio outperformed (or underperformed) a passive benchmark — for Disclosed Capitol, the S&P 500 index. It is computed per-trade and aggregated to per-politician.

Per-trade alpha (N-day) formula: alpha_N = trade_return_N − sp500_return_N where both returns are measured from the transaction_date (NOT the disclosure_date) over an N-day window. Disclosed Capitol publishes alpha_30d, alpha_90d, alpha_180d, and alpha_1yr.

Per-politician alpha is the trade-size-weighted average of all their enriched buy/sell trades. Sells contribute as "alpha avoided" — if a senator sold a stock that subsequently dropped, that's positive alpha against an investor who held.

For options trades, the underlying ticker's return is used, scaled by an implied leverage factor derived from strike + expiration. Members who concentrate in deep-OTM short-dated options have outsized alpha numbers — Disclosed Capitol flags this with a "leverage" indicator on the trade.

A politician with consistent positive alpha over 100+ trades is statistically unlikely to have produced that pattern by chance. Nancy Pelosi's portfolio is the most-cited example: her trade-weighted 1-year alpha has consistently exceeded +15% versus the S&P 500.