Buyers brave enough to go after the big deals amid the onslaught of the credit crisis this year have had to deal with an extra headache - a hit to their stock price after the announcement, a new study shows.The shares of acquirers in the top 20 U.S. deals have seen an average decline of 5.5 percent since the announcement of the transactions, according to a Lab Thomson report this week.  

The Lab Thomson study, which was conducted by Michael Thompson and Richard Peterson of Thomson Reuters, looked at deals including such takeover announcements as NRG’s bid for Calpine, Hewlett-Packard eyeing Electronic Data Systems and CME’s planned buy of NYMEX Holdings.

The study shows bidders in seven of the top 10 deals have seen their share price fall after the announcement. Five, including Delta, CME and Bank of America, have seen double-digit percentage declines.

Deals in real estate and financials sector have generally resulted in lower share prices, the study shows.

But buyers in some sectors have done better than the others.

Bidders in the energy sector, such as NRG Energy, Smith International and Grey Wolf, have seen share prices move higher, the study shows. They also account for the bulk of the nine bidders whose shares have actually outperformed the S&P 500 index since the date of the announcement.

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