The return on my IBKR foreign stocks is easily calculated since there is a report function. I also have some foreign ETFs in SCB and if I have the time I will probably look at it. At least I am holding IWDA which benefited from the rise in US markets.
As for SGX-listed stocks, I am holding quite a few counters and instead of calculating everything, I will look at my top holdings. I see that Comfort Delgro has been hit hard. My average entry price is around $1.60 (guesstimate) accumulated during the GFC and I have not added anything. Maybe next year I will do some DCA as I believe S$ will weaken meaning CDG will benefit as it receives income in other currencies as well.
Any loss in CDG should have been more than offset by gains in other shares as well as purchases through 2016 (GLP was my biggest local winner - all bought under $1.80, now $2.20). Therefore, I will take the STI ETF return as the return for my portfolio, i.e. about 3% due to dividends.