The classic 3-fund portfolio is Total Stock market, Total Bond market, and Total International (stock). While expense ratios are important, I wouldn't advice 0% international just because the expense ratio is 0.12% vs 0.05%. If you put one third into international, and have just one year of contributions, that's probably about $18,000 x 1/3rd = $6,000. The expense ratio is $7.20/yr for international vs $3/yr for S&P 500. It's definitely worth $4/year to diversify an $18,000 portfolio to international.