I was contemplating that if I wanted to diversify better, I'd invest in the C,S,I,G,F funds in my TSP (maybe 30 30 20 10 10 allocation or something similar), and invest in the sector funds with my ROTH IRA in Vanguard, like REIT, Health Care, Energy Funds, Metals, etc. But then I realized something - I'm already investing in these sectors. In my ROTH IRA, I invest i nthe Total Stock Market fund, which already invests in all of these sectors, so no need (12.8% Health Care, 8.9% Oil and Gas, for instance). The C, S, and I funds, also invest in these sectors as well. Heck, even the Total Stock Market index double dips on itself by investing in both Exxon, Wells Fargo (for example) and Berkshire Hathoway, which also invests in Exxon and Wells Fargo.