The bottom line of investing issue is measuring the portfolio performance. It's very important for the investor who or whose manager is managing the money. Important for investors who manage their own money or have another manager to manage that investment for themselves. The performance of a Portfolio must be evaluated before the intelligent decision can be made about the portfolios as the main condition is is before investing in a Portfolio the future performance of a Portfolio should be measured and then the decision should be taken. Ratings of an investment opportunity or security reflect the past performance and can be helpful for an investor. Ratings don't reflects the future performance of an investment opportunity or security though it reflects only the past performance of the investment opportunity of a security