*If the market now returns 2x the average, say 10% per year, it will take 10 years to get back to 1500 - 2020 is almost exactly 20 years.*

Dude, without a calculator...the rule of 72. 72 divided by 10% equals 7.2 years. Thus 2016 is when you should get back to 1500. But you are pretty close. The S&P500 hit a 12-year low last month, so add 7.2 years and you get pretty close to 20 years. Remember though that the market does not move in a linear fashion. Cheers!