Some food for thought
Your STI ETF DCA performance is very much dependent on when u exit (price of STI ETF, primary criterion) as well as when u start DCA and how u DCA (monthly start price, etc).
This is true. That is the reason why this exercise did a rolling study. To see all the possible returns from all possible windows of various ending months for various period.
Look at the following examples (simulated case studies) of DCA:
Mthly $100 invested using start of mth price, valued at start of mth price after end of period, annual return using the calculator here (
http://www.calculator.net/interest-...xtrate=0&cinflationrate=0&printit=0&x=51&y=17)
1. May 2002 to April 2016 (14 years, since inception of STI ETF): capital 16,800 vs market value 19,528.75 = < 2.2%
2. May 2006 to Jun 2016 (10yrs): 12k vs 11,822.3 = loss
3. Jan 2009 to Jun 2016 (7.5yrs): 9k vs 8,867.21 = loss
4. Jan 2009 (7.5 yrs) with dividends reinvested = 9k vs 10,145.69 = < 3.2%
5. Jan 2011 to Jun 2016 (5.5yrs): 6.6k vs 6100.35 = loss
6. Jan 2011 (5.5yrs) with dividends reinvested = 6.6k vs 6742.22 = < 0.8%
7. May 1996 to Jun 2016 (20yrs): 24k vs 31368.10 = < 2.6%
1) Your data above are biased. You specifically picked NON FAVORABLE windows just to prove that DCA does not work. I can also pick many more FAVORABLE windows to prove that DCA does work in the long term as what my general findings have mentioned. My FAVORABLE windows will outnumber your NON FAVORABLE windows for sure. 
2) Month end or month begin? It doesn't matter. Because there is no study that can prove convincingly that the prices at month end are lower/higher and prices at month begin are lower/higher. They will be random. You can be buying at the month low prices at the beginning or you can be buying at the high prices at the beginning of the month. 1 thing for sure, you cannot be so UNLUCKY. actually it doesnt matter if you still believe that SG market is going to do well and trend is higher in the longer term. this is the basic assumption that you must have before you DCA.
3) Among all the 20-year windows, only about 5 windows ending late 2008 and early months of 2009 were generating <0% in annualized returns. That means if you had been DCA for 19.X years and it happened to be a down market, DONT try to redeem your shares at the bottom. You have 2 options. Defer your redemption, continue to DCA for the next few months OR at least defer your redemption. ie dont sell your STI ETF yet. Of course, you must believe that the market will recover after a big crash.
Someone asked if STI continues to be range bound for the next 10-20 years, what would be the return? Take the results of 2009 (7.5yrs) add to results of 2006(10years) assuming STI rangebound in that pattern, it will still be a loss! Or rangebound with the pattern of 2011 to 2016, add 2009 and 2x 2011 results = 18.5 yrs, it is still a loss! Only consolation is your dividends? Only a simplified view of things!
Again it depends on what you believe. If you are like some of the forummer like yyhwin who predicts doomsday, then don't DCA at all.
If history is any indication of future performance?
Yes. My rolling returns for various windows for a long term DCA have shown.
The best is for people who have been doing DCA to share their portfolio results to confirm. Share your real cases to confirm the exercise being done here. Someone shared his portfolio from 2014 in another thread and read what he got in return?
Again you are picking a selected window just to discredit this method. This exercise covers ALL the possible windows you can ever imagine.