Vanguard and Fidelity Expect Less Than Half the Stock Returns of the Past Decade. Here's the Math for a 66-Year-Old With $2 Million and $4,000 a Month in Social Security.

Vanguard's new forecast puts U.S. stocks at 4.8% to 6.8% a year for the next decade and Fidelity's 20-year number is 5.8%, less than half the 15.2% the S&P 500 fund returned over the past ten years. Here is what that does to a 66-year-old couple with $2 million and $4,000 a month in Social Security: the balance at 76 at each return, whether the 4% rule still holds, and why bonds now cost almost nothing to own.