on IPO day, the IPO's bankers will buy up shares, "providing support" for the stock at a given price. it looked like management's preferred price point was $80

on IPO day, the IPO's bankers will buy up shares, "providing support" for the stock at a given price. it looked like management's preferred price point was $80 for most of the day, so the underwriters were buying at that price point. the greenshoe agreement helps the bankers buy at that point without actual economic exposure to the IPO (worth reading the wikipedia article if you're interested here). one explanation might be that the bankers bought up their entire allocation by the end of the day, which allowed price to drop to 78 in closing minutes. after day 1, who cares, the bankers already got paid.