European stocks fell, with the Stoxx Europe 600 Index posting its biggest monthly drop since August, as the number of Americans applying for unemployment insurance payments rose and U.S. business activity slowed.

The Irish vote on the European Union’s latest treaty today, with polls indicating they will endorse measures designed to ease the euro region’s debt crisis.

European Central Bank President Mario Draghi said the ECB cannot fill the “vacuum” of the lack of fiscal prudence and governance in the euro area and called for Europe’s leaders to outline where they see the euro region in the future.

Business activity in the U.S. expanded at the slowest pace in more than two years in May as orders and production cooled.

National benchmark indexes fell in all of the 18 western European markets today, except the U.K., France, Greece and Austria. Germany’s DAX dropped 0.3 percent, the Swiss Market Index fell 0.9 percent, while France’s CAC 40 rose 0.1 percent. The U.K.’s FTSE 100 added 0.2 percent

ABB, the biggest supplier of mobile power stations, declined 2.9 percent to 15.21 Swiss francs. The company will probably fail to reach the upper end of revenue targets for its low-voltage subsidiary on lackluster demand from China and Italy, said Tarak Mehta, the head of the unit.

Logica jumped 66 percent to 1.37 euros in Amsterdam after Montreal-based CGI announced it had reached an agreement to buy the U.K. computer-services provider in a 1.7 billion pounds cash transaction, offering a premium of 59.8 percent to its closing price yesterday.