NEW YORK ( TheStreet) -- At a time when investors have been making withdrawals from stock funds, cash has been pouring into top-performing world-allocation funds. Ivy Asset Strategy ( WASAX) and BlackRock Global Allocation ( MDLOX) each have attracted more than $5 billion in new investments this year, according to Morningstar. Holding a mix of stocks and bonds, the funds gained attention by avoiding the worst losses in market downturns and delivering strong long-term results. During the past five years, Ivy Asset has returned 14% annually, outdoing the S&P 500 Index by 14 percentage points and surpassing 95% of its world-allocation peers. In the same period, BlackRock has returned 8.1%. The results are intriguing. But before you invest, consider the risks. Both funds place big bets, emphasizing government bonds one year and emerging market stocks the next. That aggressive approach is different from the strategy followed by classic balanced funds, which always keep about 60% of assets in stocks and 40% in high-quality bonds. Plenty of financial advisers frown on the idea of rapidly shifting allocations. All too often investors buy and sell at the worst times, advisers say. But, most often, BlackRock and Ivy have proved to be deft traders. By putting some assets into one of these allocation funds, you may be able to diversify your portfolio and possibly reduce risk. Of the two funds, Ivy Asset is the more aggressive choice. The fund can invest in almost anything, including gold, currencies, and stocks and bonds from around the world. When markets look expensive, the managers can shift away from equities entirely or sell stocks short, betting that prices will fall. In late 2008, the Ivy managers dumped stocks, putting 45% of assets in cash. The move helped the fund outperform the S&P 500 by 11 percentage points for the year.