Some people doubt this has to do with demography ... but that's almost always predicated on the idea that in-retirement spending outpaces in retirement earnings ... the persuasive argument to counter this is that the rapid inflation in care costs combined with increased expectations of post retirement lifespan means that all but the wealthiest retirees worry about running out of money as they approach retirement ... this means that they do not dissave ... they hoard cash and bonds and some stay working ... flattening the curve and driving rates to zero is supposed to force them to dissave ... but often they simply work and save more ... this isn't a liquidity trap is a velocity trap ...