In our study, we also divide the sample of IPOs into groups of high and low subscription ratios. The high subscription ratio group consists of IPOs of which the subscription ratio is higher than 2.

Tunisian investors believe that IPOs with low subscription ratio are overvalued.

Therefore, they penalize IPO firms with low subscription ratio by a massive selling after listing.

They observe that the subscription ratio is over 91 (means).

Chahine (2007), Cheung and Liu (2007) and Ben slama et al (2011) measure the pre-IPO investors' demand by the subscription ratio which is equal to the number of shares requested by all investors in the subscription period divided by the number of offered shares.

The subscription ratio (mean = 6.21) is relatively smaller than in other international markets (Brennan and Franks, 1997; Cheung and Liu, 2007; How et al, 2007; Low and Yong, 2011) and very similar to the one found by Derrien (2005).

The coefficients on the subscription ratio are positive and highly statistically significant until the eighth week.

In the second regression, we incorporate the low subscription ratio (LSR) and the number of days from the subscription period deadline to the listing day (N) as control variables in the first regression.

This can be explained by the investors' demand (subscription ratio) and the deliberate price discount on the alternative market which are higher than that on the principal market.

From this table, we also find that the high subscription ratio group earns an initial involuntary underpricing of 18.07%, while, the low subscription ratio group earns an initial involuntary underpricing of -12.27% which is very lower than it is for the first group.