There are, I believe, five factors that help explain why security analysts have such difficulty in predicting the future. These are (1) the influence… - Burton Malkiel

Before we can determine a rational basis for making asset-allocation decisions, certain principles must be kept firmly in mind. We’ve covered some of them implicitly in earlier chapters, but treating them explicitly here should prove very helpful. The key principles are: 1. History shows that risk and return are related.
2. The risk of investing in common stocks and bonds depends on the length of time the investments are held. The longer an investor’s holding period, the lower the likely variation in the asset’s return.
3. Dollar-cost averaging can be a useful, though controversial, technique to reduce the risk of stock and bond investment.
4. Rebalancing can reduce risk and, in some circumstances, increase investment returns.
5. You must distinguish between your attitude toward and your capacity for risk. The risks you can afford to take depend on your total financial situation, including the types and sources of your income exclusive of investment income.

Most people need insurance. Those with family obligations are downright negligent if they don’t purchase insurance. We risk death every time we get into our automobile or cross a busy street. A hurricane or fire could destroy our home and possessions. People need to protect themselves against the unpredictable.

Investors should certainly be aware of new methods of portfolio construction. And high net worth investors might consider adding a multifactor smart beta offering or a risk-parity portfolio to the overall mix of their investments. Factor investing can potentially increase returns at the cost of assuming a somewhat different set of risk exposures than those of a standard broad-based index fund. And investors who are able to accept the added risks inherent in leverage might profitably add a risk-parity portfolio to their set of investments. Such offerings should only be considered, however, if they are low cost and if their potentially adverse tax effects can be offset in other parts of the overall portfolio. And I continue to believe that a broad-based total stock market index fund should be the core of everyone’s portfolio. Certainly, for investors who are starting to build an equity portfolio in planning for retirement, standard capitalization-weighted index funds are the appropriate first investments they should make.