The global stock market is weighted the following way (Larry Swedroe, The Incredible Shrinking Alpha, 2000, Chapter Seven):

• 50% US
• 37.5% International Developed
• 12.5% Emerging Markets

As Paul Merriman explained earlier, you want to allocate (1.5 * age)% into Total Stock Market (TSM), and 100 - (1.5 * age)% into Small Cap Value (SCV).

That means you want to weigh TSM and SCV according to their global weights for maximum diversification.

For example, I am 38 years old. That means I want 1.5 * 38 = 57% Total Stock Market and 43% Small Cap Value.

Therefore I would want to allocate to capture diversification:

Total Stock Market

• TSM US - $VTI - .57 * .50 = .285 = 28.5% into $VTI
• TSM International Developed - $VXUS - .57 * .375 = .21375 = 21.38% into $VXUS
• TSM Emerging Markets - $VWO - .57 * .125 = 0.07125 = 7.13% into $VWO

Small Cap Value

• SCV US - $AVUV - .43 * .50 = 0.215 = 21.5% into $AVUV
• SCV International Developed - $AVDV - .43 * .375 = 0.16125 = 16.13% into $AVDV
• Value Emerging Markets - $AVEM - .43 * .125 = 0.05375 = 5.38% into $AVEM

Do this calculation for all 6 combinations and allocate your portfolio accordingly. Rebalance once a year according to your new age, or else buy and hold for life and just buy according to your age weights.