I personally try to match global equity markets. I do that by investing in VXC and VCN in Canada, but I couldn't help but put 10% in VCN for some home bias. VXC tracks US, International developed and emerging markets making it easy for me. Not sure if there is a US version of this fund, probably a US fund and then another that tracks all International. Split 50-50 or thereabouts. Jack Bogle the ol man himself suggests sticking with US only. All roads lead to Rome and all that, just pick one and stick with it.