> Stocks can and have fallen more than 15% in this window. Possible, but not common or likely. The shares are granted at the end of one trading day (which will

> Stocks can and have fallen more than 15% in this window. Possible, but not common or likely. The shares are granted at the end of one trading day (which will be the close of that day if that's lower than at the beginning of the period) and are available for sell the next trading day. e.g. my last ESPP grant was on a Friday and I sold my shares at the open on the following Monday. So for someone to lose money through the ESPP the stock a) would need to be lower at the end of the period then the beginning and b) drop 15% at the open. Let's say such a move happens once a year to the average stock, there are about 250 trading days in a year so you have a 0.4% chance of that happening. (realistically it's probably even lower than that since drastic moves like opening down 15% are much more likely to occur following an earnings announcement than on an average day and ESPP grants and earnings aren't aligned)