When skyscrapers go up, the economy is often on its way down. That's the conventional wisdom in London, where the construction of major towers has tended to presage economic decline. For example: In 2004, Britain was chugging through its 48th consecutive quarter of growth, while Swiss Reinsurance was moving into a 40-story tower. Four years later, the country had plunged into a recession. Similar occurrences have happened in the U.S. and Dubai.