The ability to withdraw IPOs when demand is weak can increase expected proceeds for issuers. The SEC adopted rules in 2001 to make this process easier. The option value of withdrawing can be more beneficial than the underpricing associated with bookbuilding. This means that companies might choose bookbuilding even if they could sell at a fixed price for full value. The option value increases faster than underpricing when there is uncertainty, affecting the timing of IPOs and leading to hot IPO markets.