Bursting the Bubble Tulips were the first, but they won’t be the last. What forms a “bubble” and what causes them to burst? Share | Related Content Inflation and Your Portfolio Even low inflation rates can pose a threat to investment returns. The ABCs of Zero Coupon Bonds Understanding some basic concepts may help you assess whether zero-coupon bonds have a place in your portfolio. Keys to Investing for Retirement There are some key concepts to understand when investing for retirement.