I'm not sure (I've always done a traditional and just opened a Roth this year, only partially funding it), but my son is 18, likely won't pay any taxes this year and very minimal next year, so I'm having him put $1k to $2k into it, then $10/week after that. With him starting at 18, he can put just a little away and have a big payoff later. As he gets older and makes more money, he can open a traditional as well, taking advantage of both.