Clustered Insider Buying
Mechanism. Insiders buy with their own money when they believe the stock is undervalued; purchases by several
insiders in a short window are far more informative than a lone purchase, and the market takes weeks to fully
incorporate them (Seyhun 1986; Cohen, Malloy & Pomorski 2012 on opportunistic trades).
Hypothesis. Stocks where multiple distinct insiders made open-market purchases in the trailing 30 days
outperform overnight; large net insider selling relative to float underperforms.
Signature feature. Number of distinct insiders with open-market purchases (transactionType P-Purchase,
acquisitionOrDisposition = A) in the trailing 30 days. Secondary: net dollar value bought minus sold, scaled by
market cap; officer/director flag weighting.
Data. insider-trading/latest paged feed (1000 rows per page; page until you cover 30+ days and publish it
as a shared dataset), insider-trading/search?symbol= for gaps, shares-float.
Implementation sketch. Aggregate the feed by symbol: distinct buyers, distinct sellers, net dollars; score =
2*rank(distinct buyers) + rank(net dollars / mcap); names with no activity get a neutral score. Sector-neutralize.
Falsification. Top-decile sector-neutral overnight excess not positive after 40 days.