Calculation of Percentage Change in item

Hi, everybody, i'm newbie.

Recently I just found that there is a 2 way to calculation the percentage change in item.

For example, I found that in the share market, let say stock A, the open price of stock A is 5, the closing price is 8, so to calculate the change price in percentage should be ( ( 8-5 ) / 5 ) * 100% = 60%.

But I found another calculation, let say your income increase 10000 from the base rate of 50000. so to calculate the percentage change in income, that is ( 60000 - 50000 ) / ( (60000 + 50000 ) / 2 ) = 18.2%.
But if I using the above example's calculation, that is ( ( 60000 - 50000 ) / 50000 ) ) * 100% = 20%.

Actually, which calculation is correct? which one is more prefer ?

verticalforce

I had always use the first one, never heard of the second.

[ Last edited by  verticalforce at 18-3-2007 01:51 AM ]