According to https://www.iposcoop.com/the-ipo-buzz-a-dirty-dutch-auction/ https://www.iposcoop.com/the-ipo-buzz-a-dirty-dutch-auction/ "the mean average of all

According to https://www.iposcoop.com/the-ipo-buzz-a-dirty-dutch-auction/ https://www.iposcoop.com/the-ipo-buzz-a-dirty-dutch-auction/ "the mean average of all 21 [auction IPO] opening-day gain[s] was 1.25 percent". So it seems like Google was an anomaly, but Dutch IPOs in general are not leaving much money on the table compared to traditional IPOs.