The reader should verify that if the principal in the previous example earned a simple interest rate of 5.75% then the compound amount after 3.5 years would be only $3774.88. Thus happily for the depositor, compound interest builds wealth faster than simple interest. Frequently it is useful to compare an annual interest rate with compounding to an equivalent simple interest, i.e. to the simple annual interest rate which would generate the sample amount of interest as the annual compound rate. This equivalent interest rate is called the effective interest rate. For the amounts and rates mentioned in the previous example we can find the effective interest rate by solving the equation