During the late 19th and early 20th centuries, Japan became a regional power that was able to defeat the forces of both China and Russia. Japan attacked US forces in 1941, triggering America's entry into World War II, and soon occupied much of East and Southeast Asia. After its defeat in World War II, Japan recovered to become an economic power and a staunch ally of the U.S. Government-industry cooperation, a strong work ethic, mastery of high technology, and a comparatively small defense allocation (1% of GDP) helped Japan advance with extraordinary rapidity to the rank of second most technologically powerful economy in the world after the US and the third-largest economy in the world after the US and China, measured on a purchasing power parity (PPP) basis. One notable characteristic of the economy has been how manufacturers, suppliers, and distributors have worked together in closely-knit groups called keiretsu. A second basic feature has been the guarantee of lifetime employment for a substantial portion of the urban labor force. Both features have now eroded. In 2002-06, growth improved and the lingering fears of deflation in prices and economic activity lessened. Japan's huge government debt, which totals 176% of GDP, and the aging of the population are two major long-run problems. Some fear that a rise in taxes could endanger the current economic recovery. Debate also continues on the role of and effects of reform in restructuring the economy, particularly with respect to the 2007-17 privatization of Japan Post, which has functioned not only as the national postal delivery system but also, through its banking and insurance facilities, as Japan's largest financial institution.