There are many ways to invest, and this simulation considers two of them.

Consider wanting to invest $X. You can invest an amount, $a, every so many days, d, such that d*$a = $X. You could also, of course, just invest $X at the start.

The first way mentioned is basically called Dollar Cost Averaging. The second way is called Lump Sum.

I considered $200 being invested every 30 days for a year and compared the results to a $2400 (=12*$200) lump sum payment. Of course, each realization should be compared under identical market conditions, which would vary randomly from simulation to simulation. Also, the commissions (say $10 per trade) should be taken into account, with Dollar Cost Averaging having 12*$10 = $120, and Lump Sum having $10.

Valid issues like the dollars not yet invested earning interest were not considered for this simplistic simulation.

Here is a typical screenshot:

From watching the simulation many times, it is clear the winner depends on the market conditions. Obvious? Yes. But it is nice to have a clear, and free, demonstration of these facts.

The Dollar Cost Averaging Vs Lump Sum simulation is available here.