Brad,

OK. If the short column is always column 1, then you could use this to
calculate all tables:

Sub ScratchMacro1()
Dim iCount As Long
Dim oCell As Cell
Dim oCol As Column
Dim oTable As Table
Dim X As Long
Dim i As Long
For i = 1 To ActiveDocument.Tables.Count
Set oTable = ActiveDocument.Tables(i)
Set oCol = oTable.Columns(1)
iCount = -1
X = oTable.Rows.Count - 1
For Each oCell In oCol.Cells
If oCell.Range.Characters.Count 1 Then
iCount = iCount + 1
End If
Next
oTable.Cell(1, 1).Range.Select
Selection.InsertAfter " " & Round((iCount / X) * 100, 2) & " %"
Next
End Sub

If the short column could be column 1 or 2 then I am currently stumped.
I'll keep charging and see if I can come up with a solution.