If you’d like more control over your asset allocation, consider a two-fund portfolio. With just two well-diversified index funds, you can create an excellent investment portfolio.
For example, you could put your stock allocation into a total market index fund that covered both U.S. and international companies. You could then put the portion allocated to bonds in a total bond index fund. This portfolio makes it extremely easy to implement the stock/bond allocation you prefer.
Using Vanguard mutual funds as an example, here are two funds one could use to implement a two-fund portfolio:
At first glance such a portfolio might not seem to offer enough diversification. The Vanguard Total World Stock Index Fund, however, invests in over 8,400 companies. Further, these companies are headquartered throughout the world. Likewise, the Vanguard Total Bond Market Index Fund invests in over 9,000 bonds. In short, even this two-fund portfolio is well-diversified.