strikethree

Check out DFA. That little cult seems to think they have it down. Yes, I'm aware they don't use ETFs, but similar philosophy.

The thing about tactically managing a portfolio of ETFs is you're entirely top-down, and essentially market timing. Two things very few people are good at, and hardly anyone is good at both.

Limiting yourself to just category ETFs instead of industry and sector ETFs would be even more difficult. That said, if you want to beat the world index over time, just overweight emerging markets and small cap. On a risk-adjusted basis you'd probably get creamed, but on an absolute basis, I'd bet over 10 years you'd beat the index easily.

Good luck with that.