Bursting the Bubble Tulips were the first, but they won’t be the last. What forms a “bubble” and what causes them to burst? Related Content Does Your Portfolio Fit Your Retirement Lifestyle? Lifestyle considerations in creating your retirement portfolio. RE: Retirement How does your ideal retirement differ from reality, and what can we do to better align the two? Roth 401(k) vs. Traditional 401(k) This calculator compares employee contributions to a Roth 401(k) and a traditional 401(k).