Signs are good for growth in the global marketplace, largely because of the prospects for emerging markets like India and China. In the latest McKinsey Quarterly , Richard Dobbs , Susan Lund , and Andreas Schreinerare warn that there is some reason to be concerned about all that growth. Their primary concern: the availability of capital to fuel all the growth. Growth depends on investment, which depends on capital. Take a look at the McKinsey Global Institute's projections for global demand on investment over the next 20 years: Dobbs, Lund, and Schreinerare note that when economies become more robust, the savings rate declines. And therein lies the problem for investment capital: The capital needed to finance this investment comes from the world's savings. Over the three decades or so ending in 2002, the global saving rate (saving as a share of GDP) fell, driven mainly by a sharp decline in household saving in mature countries. The global rate has increased since then, from 20.5 percent of GDP in 2002 to 24 percent in 2008, as household saving rebounded in mature economies and many of the developing countries with the highest rates-particularly China-have come to account for a growing share of world GDP. Our analysis suggests, however, that the global saving rate is not likely to rise in the decades ahead, as a result of several structural shifts in the world economy. First, China's saving rate will probably decline as it rebalances its economy so that domestic consumption plays a greater role. In 2008, China surpassed the United States as the world's largest saver, with the national saving rate reaching over 50 percent of GDP. But if China follows the historical experience of other countries, its saving rate will decline over time as the country grows richer, as happened in Japan, South Korea, Taiwan, and other economies (Exhibit 2). It is unclear when this process will begin, but already the country's leaders have started to adopt policies that will increase consumption and reduce saving. 4 If China succeeds at increasing consumption, it would reduce the 2030 global saving rate by around two percentage points compared with 2007 levels-or about $2 trillion less than China would have accumulated by 2030 at current rates. Read How the growth of emerging markets will strain global finance here .