I'm trying to count the number of new categories that I added to my inventory each year. I'm currenty using countif(Range, ">0") and then subtracting the results from previous years, but I'm having to offset this because sometimes I because I have zero of that item in a subsequent year (e.g., Category 2, 2014). Is there a way I can write a formula to count new categories added by year easily?

For results, I'm expecting 2 for 2013 (since 2 new categories were added), 1 for 2014 (since only Category 3 is a new category), and 0 for 2015 (since no new categories were added).

2013 2014 2015
Category 1 1 4 0
Category 2 2 0 6
Category 3 0 5 1