Using search terms defined by Robert A. Muenchen here, I created a simple dataset. I simply limited the publication to one year, searched using the defined terms. Each manual search (as of 13-Jan-2019) had a row with tool, year and number of results recorded. The options for patents and citations were de-selected.

Of course there are limitations to the quality of the data retrieved using this simplistic approach. A better solution would be Harzing's Publish or Perish. Unfortunately, that tool limits a query to 1000 citations. As you can see, the current project far excedes that limit. However, I feel it is sufficient to get a general sense of the trends over the past 10 years.

Y Axis calculation