Nearly all insiders (i.e. management, investors, employees, etc.) will be subject to a "lock-up" on an IPO that prevents them from selling immediately. Typicall

Nearly all insiders (i.e. management, investors, employees, etc.) will be subject to a "lock-up" on an IPO that prevents them from selling immediately. Typically the lock-up lasts for 180 days, but this can vary. Share price does often drop when the lock-up expires, but usually not as much as you'd expect--the number of restricted shares to be release and resulting liquidity effects of that expiration are well know and disclosed in public filings. So this mostly gets baked into pricing well in advance.