ETFs: What to Buy in a Growing Economy

Exchange traded funds account for nearly a third of U.S. stock market trading in dollar terms these days, with some 2,000 ETFs to choose from. How do ETFs fit into a

well-designed portfolio, and which ETFs should savvy investors buy?

We asked three of our top columnists -- Stocks Under $10 co-manager Stephen "Sarge" Guilfoyle, Trifecta Stocks Co-Manager Bob Lang and Income Seeker Manager Peter Tchir -- to weigh in.