You can calculate the percentage of one group within a broader grouping. For example, you could show the sales in each city as a percentage of the total sales for each country. Or, you could show each country's percentage contribution to the grand total of sales.
To calculate a percentage
Note The "sum" calculation appears in the list only when a field containing numeric data is displayed in the first drop-down list.
Note : The summary location cannot be Grand Total (Report Footer) when you are calculating a percentage.
You can choose to show a percentage of a group within another group, or to show a percentage of the grand total.
The summary percentage field is added to your report.