Finding the percentage of ratings that show changes.

[SASuser4321]

I have two columns in a table. 
I need to find the number of rows in which Rating_a is not equal to Rating_b and then divide that number by the total number of rows in the table. Basically, I need to find the percentage of where the values differ. Could someone please help me with this? I think using the COUNT function could work. Help would be appreciated. Thank you.
Here's a sample (actual table has 1000s of rows) of how it looks like:

Rating_a	Rating_b
1	1
2	3
4	4
4	1
3	3

[Kurt_Bremser · Accepted solution]

proc sql;
select sum(rating_a = rating_b) / count(*) as percentage format=percent7.2 from have;
quit;

[SASuser4321]

To show changes, one would have to write "rating_a ne rating_b" instead of using the = sign. But thank you for your answer. I understood it and it works and I'm accepting it 🙂

[PaigeMiller]

Would there ever be missing values? How would those be handled?