Some of the many recent assessments of how much American workers should save and when they should save it underestimate the sufficiency of retirement savings for many households, according to a decidedly contrarian report from Towers Watson.

In "American Workers' Retirement Income Security Prospects: A Critique of Recent Assessments," authors Gaobo Pang and Sylvester J. Schieber argue that some these assessments rely on models that don't adequately reflect changes over a worker's life cycles.

"They extrapolate younger workers' observed savings behavior into the future, ignoring workers' capacity to catch up after children leave home, the mortgage is paid off, and other early-life obligations have been discharged," Pang and Scheiber said.