Institut numerique

I-1\\ The model:

As I presented in the previous sections, there are numerous explanations advanced to
understand and to clarify the short run IPO anomaly. These explanations can be classified in
three main categories:

 Explanations based on asymmetric information between the key IPO parties and have
been considered the most convincing explanations for decades.

 Explanations asserting the informational transparency and lucidity and asserting the IPO
market efficiency.

 And explanations based on Behavioral Approach and on investors’ sentiments and
beliefs.

I regroup the three theories advanced in the same model to determine which of these
explanations characterizes best the data in the context of a unified model and presents the
most relevant and reliable explanation to underpricing phenomenon. I present every theory by
one or more indicators and determinants.

 For the informational asymmetry theory, I use the firm quality as a determinant with
many proxies: the Overhang Ratio, Venture Capital backed, Underwriter reputation and
R&D intensity.

 For the theory asserting the IPO market efficiency, I use the risk determinant: age of the
issuing firm, firm size (sales and assets), firm profitability, ROA and the issue risk (if
the firm operates in a technological and risky sector). I use also the issue size (Ln
(expected proceeds)), and the issuer bargaining power.

 Finally, for the behavioral approach, I use direct measures of investor sentiment, and I
distinguish between the two types of investors: the individual investor sentiment and the
institutional investor sentiment. For this, I use the individual investor sentiment index
(AAII) and the institutional investor sentiment index (II).

The regression model used in this study is as follows:

Underpricing = a0 + a1Underwriter Reputation Dummy + a2Overhang + a3R&D
Intensity + a4VC Dummy + a5Ln (1+age) + a6Ln (assets) + a7Ln (sales) + a8Firm
Profitability + a9ROA + a10Issue Risk Dummy + a11Ln (expected proceeds) + a12Insiders
Ownership + a13Institutional Ownership + a14Blockholders Ownership + a15Individual
Investor Sentiment + a16Institutional Investor Sentiment+ a17Time Dummy + εi

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