If you are familiar with legendary fund manager Peter Lynch and his must read book, One Up On Wall Street, you know exactly what “Buy what you know” represents. The Fidelity Magellan Mutual fund averaged an annual return of around 30% while Lynch was its portfolio manager between 1977 and 1990. Lynch was a big believer that even the average investor could achieve great success by investing in companies and industries that they have some type of relationship with.