Insider Sell Ratio · S&P 500 (30 days, Form 4)

## What this measures

Of the open-market trades that officers, directors and 10% owners of S&P 500 companies reported to the SEC over the trailing 30 days, the share that were sales: sale events ÷ (purchase events + sale events). An event is one filing's purchases (code P) or sales (code S) on one transaction date. One point per day.

## Why it matters

Insiders sell for many reasons (diversification, taxes, pre-arranged plans) and buy for one. The ratio is normally high; what carries information is when it falls, meaning insiders across large companies are buying their own stock with their own money.

## How to read it

Normally well above 0.8. A drop toward the low end of its own history is the signal to notice, especially when it happens across sectors at once. Pair it with the dollar series (positioning.insider.sp500_net_value_usd_30d).

## What it does not say

It counts filings, not dollars: one small purchase weighs the same as one large sale. Grants, option exercises, tax withholding and gifts are excluded. Many sales are made under Rule 10b5-1 plans set months earlier (flagged on filings since April 2023). Insiders have two business days to file, so the last couple of days fill in late. Amendments are excluded, and one trade reported on separate forms by joint filers counts once. Current S&P 500 members only.

## Source

U.S. Securities and Exchange Commission: Forms 4 and 5 on EDGAR, and the SEC Insider Transactions Data Sets for history (https://www.sec.gov/data-research/sec-markets-data/insider-transactions-data-sets). Public domain. Until 2026-09-25 this series read a vendor's partial Form 4 feed; history was rebuilt from the SEC filings.

## Revision — 2026-09-26

Universe updated to current S&P 500 constituents (8 out, 3 in). Out: Builders FirstSource, Molson Coors and The Trade Desk, which left the index on 21 September 2026; Electronic Arts, which was taken private and left on 5 August 2026; and MongoDB, Cloudflare, Snowflake and Zoom, which were never members and had been included in error since May 2026. In: Bloom Energy, Everpure and Illumina, which joined on 21 September 2026. Membership now comes from a dated constituent list refreshed monthly. The corrected list applies from 26 September 2026. Readings before that date are unchanged.