Hi Rachel,
I'm not sure if this is what you need, but you could create two different standard/custom reports and change the Dates (Filtering) to collect last year's information vs this years (e.g. - 2014 Report = 1/1/2014 - 12/31/2014 and 2015 Report = 1/1/2015 - 12/31/2015).
You may need to download both reports (or see two windows side-by-side) to see the difference year-over-year.
I hope this helps.