 This allows the owner the security of knowing that the $100,000 is safe but rather than receiving the sure 4% they can receive up to 8%.Historically since 1950, an 8% cap on the S&P 500 has resulted in an average interest credit of 5.2%, very similar to what is considered the "risk free rate of return" delivered by T-bills, 5.1% over a similar period.The return may also be adjusted by other factors such as the participation rate and market value adjustments to cover bring the cost of the option into the budget available.