How to read politician trades

What a disclosure is

• Members of Congress must report trades in stocks, bonds and funds held by themselves, their spouses and dependent children. The reports are public records.
• They arrive late: up to 45 days after the trade is allowed, and the median filing here came 28 days after the trade. By the time a trade is public, the price it was made at is history.
• Amounts are dollar ranges such as $1,001–$15,000, never exact figures or share counts. That is why any gain shown on a member's page is a percentage, marked ≈, and never a dollar amount.
• Many rows are funds, bonds or private holdings with no stock ticker, and some filings are scanned images. A member's record here is what could be read, not everything they own.

What happened after trades became public

For every disclosed purchase and sale, we compare the stock's return with SPY over the same days, starting from the first close after the disclosure — the first moment anyone outside Congress could act.

Not published yet: the SPY price history every figure is measured against is still loading.

How we measure

• Each trade is dated to its disclosure, not the trade itself. Measuring from the trade date would count weeks no reader could have traded in.
• Returns are taken 5, 10, 20, 60 and 120 calendar days after the first close on or after the disclosure, on split- and dividend-adjusted prices.
• Each is compared with SPY over exactly the same dates. One plain benchmark is the honest floor for data this ragged; a factor model would suggest precision it cannot support.
• Purchases and sales are reported separately and never netted. A sale is not a short sale, so its result is shown as it is, not reversed.
• Medians come first, because a few large moves pull an average around. A horizon with fewer than 30 measured trades shows no figure at all.
• Nothing is published until price history covers 80% of the trades old enough to measure. The study reruns weekly.

What this is not

It is not a track record, a trading strategy or a prediction, and it is unrelated to ShareValue's stock scores. It describes what followed past disclosures. A small or absent difference from SPY is a finding, not a failure: it is what the evidence shows.