The euro-zone economy has undoubtedly caught some sort of bug, and investors are struggling to diagnose whether this is just a cold or a more serious case of the flu. On the one hand, business sentiment and industrial production have dropped sharply, but on the other hand consumer sentiment and spending have held up relatively well, despite higher energy prices and an uptick in unemployment. Since domestic demand will determine the depth and duration of the recent slowdown, the key data to monitor are leading indicators of consumer spending, like real wage and employment growth, and consumer sentiment.