I am doing a study in sudden death in athletes. So for every study I get a percentage that represents the number of athletes that died from a particular disease. For example:

**Study Duration / Total Number of deaths / Deaths from Myocardial Infarction (MI) / MI % / Deaths from Cardiomyopathy (CM) / CM %**

1990-2000____ / 100 _______________________ / 50__________________________________________ / 50% / 25 _____________________________________/ 25%

2000-2002____ / 1500 ______________________ / 250________________________________________ / 16.6%/ 120 ____________________________________/ 8%

1980-1985____ / 20 _________________________ / 13_________________________________________ / 65% / 7 ______________________________________/ 35%

....

1990-2000____ / 100 _______________________ / 50__________________________________________ / 50% / 25 _____________________________________/ 25%

2000-2002____ / 1500 ______________________ / 250________________________________________ / 16.6%/ 120 ____________________________________/ 8%

1980-1985____ / 20 _________________________ / 13_________________________________________ / 65% / 7 ______________________________________/ 35%

....

How can I calculate the average of the percentages in order to get an overall "average percentage" across the studies included? For this example lets say "Deaths from Myocardial Infarction" for which the percentages are 50%, 16.6%, and 65%. Obviously just to sum and divide them is not enough. Maybe for every study percentage should be a weight according to the population?

Thank you