And they left out the factor I consider, by far, the most important: the opportunity cost of missed investment gains/income from having the money eight years earlier.
If you can afford to delay SS until 70, you can also afford to start SS at 62 and use the monthly check to dollar cost average into a low cost TSM index fund (periodic monthly investment actually) for eight years. This past decade, that would have put the "take it at 62 crowd" ahead of the "delay until 70 crowd" for their lifetimes. Of course, a decade of crappy market performance would not turn out so well.......
I continue to be fascinated as to why these studies generally ignore the time value of money when it is such an important factor.