NEW YORK ( TheStreet) -- Searching for income, investors have poured into high-yield ETFs. Among the favorite choices are iShares iBoxx $ High Yield Corporate Bond ( HYG) and SPDR Barclays Capital High Yield Bond ( JNK), which both yield around 7%. Assets in the two funds total $25.3 billion, up from around $13 billion at the beginning of 2011, according to IndexUniverse.com.But ETFs may not be the best way to hold high-yield bonds, which are rated below-investment grade. The problem is that junk bonds are not highly liquid. Many bonds rarely trade. During the downturn of 2008, markets froze, and it was difficult to trade bonds at all. As index trackers, ETFs must buy bonds -- even if portfolio managers must pay a big premium to complete transactions. Instead of buying index funds, investors should consider actively managed portfolios, says Samuel Lee, an ETF analyst for Morningstar. "Active managers have the discretion to avoid trading when prices are ridiculous," says Lee.
Partly because of their freedom to trade, many actively managed mutual funds have outdone ETFs in downturns. When investors worried about the outlook for the eurozone in May, high-yield bonds sank. For the month, the iShares iBoxx ETF dropped 3.2%, while the average actively managed high-yield mutual fund lost 1.5%, according to Morningstar. The active managers also excelled in September 2011 when they lost 3.3%, compared to a decline of 5.3% for the iShares fund. During the past three years, the average active fund returned 14.4% annually, while the iShares fund returned 14.1%. Mutual funds can also have an advantage because the shares always sell for the value of the assets in the fund. In contrast, ETF share prices fluctuate. When many investors seek to buy, the ETF shares can sell for a premium to the value of the assets in the fund. During hard times, the shares can trade at a discount. Funds that hold highly liquid assets, such as the stocks of the S&P 500, rarely trade at big premiums or discounts. But the price of high-yield funds can vary. The SPDR high -yield ETF recently sold for a premium of 1.24%. So investors had to pay $101.24 to buy $100 worth of assets.