Costco insider trading

Does following Costco’s insiders pay?

From March 12, 2010 to October 14, 2026, 39 insiders reported 4 open-market purchases and 323 sales not made under a pre-set plan in Costco. Twelve months after each purchase was reported, the shares were +5.8% against the S&P 500 on average (median +1.6%), over 4 purchases with a full year of prices; 75% beat the index. After sales, the shares moved +6.0% against the index over 12 months (a negative figure means selling was the right call). That rests on fewer than 20 purchases, too few to read much into. Buying each purchase the day after it was reported, an equal amount each, held 12 months or until that insider reported a sale, would have turned $10,000 on November 11, 2015 into $13,375 by November 2, 2026, +2.7% a year. It held shares 32% of the time; the S&P 500 on those same days, with Treasury bills otherwise, made $10,640 (+0.6% a year), and held throughout $43,559 (+14.4%).

Moves are the shares’ return including dividends minus the S&P 500’s, from the close on the first trading day after each report; the number of trades with a finished 12-month window is in brackets. Green means the trade went the insider’s way (a purchase ahead of the index, a sale followed by the shares trailing it). A trade reported both by a director or officer and by a fund or company they are linked to counts once here, under the person. Purchases count only where the share price actually traded was at least $5. These figures describe what the shares did, not why anyone traded. Insiders across all companies.