我猜那个少的是税后的实际interest吧

比如interest rate 4.97%, 以天为单位计息

那一年的收益率就是（1＋4.97％/365)^365-1=5.1%

高的那个是复利

要看后一个. APY = 年实际产出率.

也就是说, 假定你存1万快1年定期, 两个银行利率(IR)一样.银行1是每3个月结算一次利息,每结算一次,利息就被加到本金中. 等下三个月再结算时, 你的本金就已经大于1万刀. 而银行2可能是6个月结算一次利息,这样你要等到6个月的时候本金才增长. 所以虽然bank1&2 IR一样, 但是1的APY要高于2. 你得到的实际利息就高.

For 4% interest rate or APR, and w/ 10K principal, lets say you put it in the bank for a year.  Then, you will get:

$10,000*(1+4%)=$10,400

Annual Percentage Rate, or APR, is a measure of how much interest will be on an annual basis without taking into account compound interest. Annual Percentage Yield, or APY, is the same measure of interest rate, but accounting for compound interest - a better measure of how much you will pay in interest. Banks and credit card issuers often express credit card interest rates in APR, in order to better hide just how much interest would cost.

Next case, if you have 5% APY, we will have to convert it to APR.  The formula is simple like this:

APR = Period Rate x Periods per Year

Therefore:

5%=((1+Period Rate)^12)-1 ==>

1.05=(1+Period Rate)^12 ==> Period Rate = .004074

Recalling APR = Period Rate x Periods (in this case, 12), then the APR is 4.89%

So, you are not getting what you might think you were based on an ads.  But 5% APY is still better than 4% APR, since you are comparing a 4.89% APR to a 4% APR (apples to apples).

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