Calculations using multiple items from the same field in a pivot table?

[zsdazey]

I have spent a lot of time searching for an answer to this, but no luck. I'm sorry if this is in the wrong place, this is my first post here.

I have a sheet with raw data (first table). Each row contains a person's name (each person appears multiple times, and there are over 30,000 rows currently). There are three columns to the right, which contain either "Yes","No","N/A", or are blank:
[TABLE="class: grid, width: 500, align: center"]
<tbody>[TR]
[TD]Employee
[/TD]
[TD]Criteria1
[/TD]
[TD]Criteria2
[/TD]
[TD]Criteria3
[/TD]
[/TR]
[TR]
[TD]Person 1
[/TD]
[TD]Yes
[/TD]
[TD]Yes
[/TD]
[TD]No
[/TD]
[/TR]
[TR]
[TD]Person 2
[/TD]
[TD]No
[/TD]
[TD]Yes
[/TD]
[TD]Yes
[/TD]
[/TR]
[TR]
[TD]Person 1
[/TD]
[TD]Yes
[/TD]
[TD]Yes
[/TD]
[TD]Yes
[/TD]
[/TR]
[TR]
[TD]Person 3
[/TD]
[TD]Yes
[/TD]
[TD]N/A
[/TD]
[TD]No
[/TD]
[/TR]
</tbody>[/TABLE]

After creating a pivot table with the data, I put the "Employee" field in row labels, and "Criteria1" in both column labels and values, returning this:
[TABLE="class: grid, width: 500, align: center"]
<tbody>[TR]
[TD]Employee
[/TD]
[TD]No
[/TD]
[TD]Yes
[/TD]
[TD]Grand Total
[/TD]
[/TR]
[TR]
[TD]Person 1
[/TD]
[TD][/TD]
[TD]2
[/TD]
[TD]2
[/TD]
[/TR]
[TR]
[TD]Person 2
[/TD]
[TD]1
[/TD]
[TD][/TD]
[TD]1
[/TD]
[/TR]
[TR]
[TD]Person 3
[/TD]
[TD][/TD]
[TD]1
[/TD]
[TD]1
[/TD]
[/TR]
</tbody>[/TABLE]

Instead, I want the pivot table to only show percentages for each criteria, and an average of all 3 percentages. Percentages should be calculated as the "Yes" number divided by the "Grand Total," to look like this:

[TABLE="class: grid, width: 500, align: center"]
<tbody>[TR]
[TD]Employee
[/TD]
[TD]Criteria 1
[/TD]
[TD]Criteria2
[/TD]
[TD]Criteria3
[/TD]
[TD]Average
[/TD]
[/TR]
[TR]
[TD]Person 1
[/TD]
[TD]100%
[/TD]
[TD]100%
[/TD]
[TD]50%
[/TD]
[TD]83.33%
[/TD]
[/TR]
[TR]
[TD]Person 2
[/TD]
[TD]75%
[/TD]
[TD]75%
[/TD]
[TD]25%
[/TD]
[TD]58.33%
[/TD]
[/TR]
[TR]
[TD]Person 3
[/TD]
[TD]100%
[/TD]
[TD]75%
[/TD]
[TD]50%
[/TD]
[TD]75.00%
[/TD]
[/TR]
</tbody>[/TABLE]

I can get the "Yes" column in the pivot table to display as "total percentage of current row," which is the correct percent, but every time I try to add more criteria it adds a ton of other columns I don't need.

How would I go about creating this pivot table?