60/40s stand the test of time

This decade, US 60/40 portfolios have been hit harder than all-equity allocations – something that hasn't been seen over the past 150 years. Mixed portfolios have historically reduced losses during downturns. The stock market crashed by 79% during the Great Depression, whereas 60/40 portfolios would’ve experienced a decline of just over 50%. Looking at the 1970s, 60/40s would have taken a 39.4% blow, less than the stock market’s decline. The stock market decreased by 54% over the 2000s, more than double that of mixed portfolios. So, why were 60/40s hit so hard this decade? Is diversification...