My guess is that the shares required for purchase are less than his salary. Perhaps it just comes directly out of there? Don't know, don't care. On this issue we were wrong, TBG was technically right although I would guess that requirement was extremely rare.
In lots of cases the company will make him a low or no interest loan to buy their shares.. Payable back when he sells the shares. The company's gain is they can tote insider buying in their PR's and SEC filings. The Market and shareholders love a company with 'insider buying' It's a win-win for everyone involved. As long as the PPS increases.
News 
Market Data 
Discover 
AI
