Hi, I'm using the bulk download to get a count of the number of yearly citations that a patent received. I am using the uspatentcitation file. However when I count the total number of citations("citation_date" in the dataset)  by year  I found a strange behaviour. I see an increasing number of citations up to 2000, then a decreasing number which became very sharp from 2014. I am considering data from 1976 to 2022.

I don't know if I made some mistake during the data-cleaning or if there are problem in the dataset. Did someone find the same result? 

Bests

Angelo