Why wouldn't the "3 month % gain (ending)" be equal to
((1+(return month1))*(1+(return month2))*(1+(return month3)))-1 ?
I've created a table with sequential 12 month returns and also included cumulative 12, 9, 6 and 3 month returns - but it looks odd. There are cases were all three months are negative returns but the "3 month % gain (ending)" is a positive number?