I've been considering whether to add Vanguard's Emerging Markets Stock Index Fund to my 401(k), Roth IRA, and taxable fund accounts. Would adding emerging markets give my accounts a boost, so to speak?

My 401(k) and Roth IRA have the same allocations. The "old allocation" was recommended to me by a financial planner a few years ago. The "current allocation" is what I have changed them to on my own, since I thought it made no sense for a 30-year-old to have short-term treasuries in retirement accounts.


Old Allocation for 401(k) and Roth:

8% Vanguard Value Index
17% Vanguard REIT Index
14% Vanguard Small Cap Value Index
16% Vanguard Short-Term Treasury
25% Vanguard Total International Stock Market Index
20% Vanguard Total Stock Market Index



Current Allocation for 401(k) and Roth:

10% Vanguard Value Index
26% Vanguard REIT Index
16% Vanguard Small Cap Value Index
26% Vanguard Total International Stock Market Index
22% Vanguard Total Stock Market Index


If adding emerging markets would be beneficial, what percentage would be adequate? And which fund holdings in the "old allocation" should be reduced to accommodate it?