
For these types of questions, you can create a PivotTable report. A PivotTable report is an interactive table that automatically extracts, organizes, and summarizes your data. You can then use the report to analyze the data to perhaps compare, detect patterns, or compute sums, averages, and counts.
For example you can use these data:

…to create a PivotTable report that shows the total units and income for each year:

Before you begin your first PivotTable report, it’s a good idea to make sure your data is well organized and ready to go. Neatness counts! For example you’ll want to be sure that the first row of the list contains column labels, since Excel will use these labels for field names in the report. If you haven't realized it yet, you are truly working with a "database" of information. A database is a collection of information that's related to a particular subject or purpose, such as tracking students or maintaining a music collection. Microsoft Access is used for working with large databases, but for smaller lists, Excel's sorting, filtering, and PivotTable functionality usually meets the needs of the user.
To create a PivotTable report, you first use the PivotTable and PivotChart Wizard to specify the data you want to use and to create the report framework. You can then use the PivotTable Toolbar to arrange the data within that framework.
PivotTable Toolbar
For example, you can choose categories of data to include (shaded in yellow) and the corresponding data values (shaded in green) that you would like to summarize or compare. In the example below, I am using the year and month as categories to summarize the total number of units.

After arranging the categories into rows and columns, Excel creates the finished report and automatically summarizes and totals data values.


There are many ways to further customize a pivot table with calculations and groupings. For more information about PivotTable reports, use Microsoft Excel's Help menu.