Grasping Reality on TypePad, by Brad DeLong

...Researchers using a life-cycle model... conclude that most pre-retirees have an optimal level of wealth.... The comforting results of the optimal savings research depend crucially on two as- sumptions--that households’ consumption declines when the kids leave home and that households plan on declining consumption in retirement.... The target replacement rate analysis assumes that consumption does not decline when the kids leave home and that retirees plan on level consumption in retirement. The question is which view best reflects the real world.

http://crr.bc.edu/wp-content/uploads/2015/03/IB_15-5.pdf