I think his formulas are based off of assumptions that don't fit reality for people. A good example is lifetime stock market average. I did a study recently where I tracked the date and cash amount of every retirement contribution I've ever made, and pretended I simply bought an S&P-500 index fund on each of those dates. I then calculated my lifetime APY, and it was nowhere near the averages that the magazines claim. I've been a pretty consistent retirement saver but the point is that my savings past tracks what is probably true for most people - I've had more to save in years where times were good (and the stock market was higher), and less to save in years where times were bad (and the stock market was lower). When you take the same formulas that he claims as gospel and plug in more reasonable "stock market average performance" each year, you get vastly different conclusions.