Depends on your investment objectives. What is your time horizon for investing? Remember, bonds can equally be important during times of market stress. YTD, the Barclays Aggregate bond index is up almost 6% compared to 4% for the S&P 500. Having a strategic asset allocation methodology can help prevent losses, such as during the market crash of 2008, when a fund invested solely in an index fund which tracks the S&P 500 would have lost 40% of its value. Would also recommend about 20% of the portfolio be invested in small & mid cap stocks.

Source: I do this for a living.