Exchange-traded funds (ETFs) have become popular with investing. One fund can hold hundreds of stocks at a fraction of the cost of a traditional mutual fund, which could help explain why U.S.-listed ETFs held about $14.21 trillion in assets as of early 2026, according to the Investment Company Institute. Read More: This ‘Boring’ Investment Could Be the Secret to Never Running Out of Retirement Income Learn More: 4 Safe Accounts Proven To Grow Your Money Up To 13x Faster   But not all ETFs may be worthy o ...