Historical Successful/Failed German IPOs last 3/5years - IPO Discount

I analysed the last 5 years of IPOs in Germany and there performance.
I screen every initial public offering in a German market since 2007.
It does not look very good for the IPO buyers, especially on the long term (3 years plus). Traditionaly people speak of an IPO discount of 15-30% given on the intrisic value to motivate investors to buy into IPOs.
However this data shows that more the opposite is true, an IPO premium of at least 15%.
Now maybe the German market is just really bad for IPO-investors. As my data shows there were only a total of 14 IPOs above a 0% performance, only 5 of them from 2008 and 2007.
In my opinon that is a pretty devastating account.

The 3 latest  years (2012-2009)
3 yr Median:                      -12,37%
3 yr Arith. Middle:            -15,60%
3 yr Variance:                     29,35%
3 yr Nr. IPOs:                     31
This is year 4 and 5, or 2008 and 2007, which shows the worst performance, probably since it includes all the IPOs from boom year 2007 where a lot of junk went public:
4 yr - 5 yr Median:           -63,64%
4 yr - 5 yr Arith. Middle: -49,51%
4 yr - 5 yr Variance:          39,97%
4 yr - 5 yr Nr. IPOs:          49
Here the total time span of 5 years:
5 yr Median:                     -52,58%
5 yr Arith. Middle:           -36,37%
5 yr Variance:                    38,58%
5 yr Nr. IPOs:                    80