Over their 50 years of marriage, Dave and Kathy Lindenstruth adopted a time-honored Wall Street strategy to safeguard and grow their retirement nest egg: a mix of 60% U.S. stocks and 40% bonds known as the 60-40 portfolio. Now, it is failing them.

“There have been some days more recently where I’ve looked at my portfolio and gone ‘oh, crap,’” Dave Lindenstruth said.