Workers might be saving money for retirement in either atraditional tax-deductible 401(k) or in a Roth 401(k), but theymight not understand the differences between the two, so they’renot making an informed decision on whichto use or how much to save in each.

That’s according to research from the National Bureau ofEconomic Research, which looked at the employee contributions at 11large companies that added a Roth 401(k) option after 2006. TheNBER study revealed that there was no significant difference intotal contribution rates between those employees hired in the yearbefore the Roth was added and those who were hired immediatelyafterward.

While a contribution of $1,000 will cost the employee less intake-home pay when going into a traditional 401(k), it will costthe whole $1,000 when going into a Roth, since the money going intoa Roth is taxed up front — while withdrawals, including investmentreturns, are not taxed on withdrawal. But employees either don’trealize that the Roth funds won’t be taxed when they withdraw themon retirement, or are too much in need of the current tax break towait that long.