Well, let’s put a caveat on that headline: that return requires that you are able to get zero-coupon T’s at the sort of yields they produced in 1981 - which for 25 years would have been north of 12%.
Which you cannot do right now. I doubt you can get zero’s at even half the yields seen in 1981.
The only way you’d achieve that sort of yield is to load up on risk in commercial bonds.