During 1990-1998, IPO underpricing doubled to almost 15% compared to the 7% average during 1980-1989, yet it reverted to 12% during the post-bubble period of 2001-2003. Explain the rationale behind such changes in underpricing, with regards to the changing risk composition hypothesis, the realignment of incentives hypothesis and the changing issuer objective function hypothesis. Refer to the Loughran and Ritter (2004) article, Why has IPO underpricing changed over time?