I decided I wanted the Prevalence to be the percentage of all tables not of all columns, so I used James Goodwin's code and modified it to get the total table count.

SELECT COLUMN_NAME, CONVERT(DECIMAL(12,2), Count(*)* 100.0/t.totalTables) as [%]

INTO #Prevalence

FROM INFORMATION_SCHEMA.COLUMNS

CROSS JOIN

(SELECT Count(*) as totalTables FROM INFORMATION_SCHEMA.TABLES ) t

GROUP BY COLUMN_NAME, t.totalTables

Select * from #Prevalence gives me useful information, all by itself.