OK, folks. It's time for a little lesson. Allow me to state that which should be obvious but which an amazing number of people have trouble understanding:
Dollar Cost Averaging IS Market Timing.
Got that?
If you decide to invest in any liquid (I can get out of the investment at any time - although perhaps with a loss) investment, then put it all in at one time - as soon as you have made the decision to invest it in that particular vehicle. Anything else (splitting it in half and waiting six months to invest the other half or any other such scheme) is taking a bet on the performance of the market in the interim. i.e., it IS Market Timing which is nearly uniformly a bad idea.
Here's the basic math. Imagine you have $200. Let the year end value of $1 invested in the market at the beginning of a given year i be denoted by ri. So $1 invested at the beginning of year 1 yields $r1 by the end of the year. Kept in the market for year two it becomes worth $ r1xr2 and so forth.
Now imagine that you take your $200 and invest it all at the beginning of year 1 and keep it invested until the end of year 2. At this time you will have $200 x r1 x r2. Note that both r1 and r2 carry equal weight in the scenario. That is, year one and year two are being treated the same as one another.
Instead, invest only half at the beginning of year 1 and the other half at the beginning of year 2. At the end of year two you will have ($100 x r1 x r2) + ($100 x r2). Note that all of your $200 is subject to the returns of the market in year 2 but only $100 is subject to the returns of year 1. That is, you are treating year one as 'special' - somehow inherently more risky (or less rewaring) than year two. I.e., you are engaging in market timing.
Try it yourself - what would it look like if you invested all of the money at the beginning and then took half out at the beginning of year two (basically the opposite of dollar cost averaging and intuitively a rather absurd strategy). It turns out that your final sum would be ($100 x r1 x r2) + ($100 x r1). In this case we really like year one and are avoiding that risky year two but this absurd strategy makes exactly as much sense as the oh so clever idea of 'dollar cost averaging' - compare the final sums above for yourself.
Bottom line - dollar cost averaging in general makes no sense and has become part of the investing culture most likely due to a lack of basic algebraic competence.
For this I will not ask for the usual 2p. Just that fact that you understand the algebra is satisfying enough.