Would it be more wise to invest in a ROTH IRA with a lump sum at the beginning of each tax year or spread out the contributions to even monthly amounts?

Dollar cost averaging FTW.

Mathematically its better to dollar cost average.  However, in this market, I would try to lump some in at the bottom which would be anyones WAG where it is.  Lumping it in every year throughout the course of 30 some years would still be dollar cost averaging in a way.  Just not as efficiently.

Unless you have a really good crystal ball, this is impossible.

I go with dollar-cost averaging.  At the beginning of the year, I divide the number of pay periods into the max I can contribute to my Roth, and I direct-deposit that amount.  It's automated, so I can't decide to skip "just this one contribution".

It would be interesting to do a historical analysis... pick a year, and go forward both ways.  You get a little bit more compounding with the lump sum, but I think the ups-and-downs of the market will negate that.  My guess is averaging would win.

Monthly DCAing works best imo/ I've lump summed twice and wished I'd had'nt. Good Luck!

i have mine set up to automatically withdraw from my bank every week. max out the annual limit