Are their historical reasons behind the waning popularity of facial hair in the U.S.A over the past century?

by Euralos

This graph was posted on /r/dataisbeautiful today.

I was curious if there were any known reasons for what appears to be a fairly consistent lessening of American facial hair from 1887 into modern times. Was this just a cultural shift, or were there actual efforts to get men to go clean-shaven?

Also, concerning the "spikes" in the chart, do any of those years coincide with special events that made facial hair more popular?

EDIT - Crap, wrong version of "there", oh well, it's stuck now

International_KB

Note that that graph was based exclusively on the pages of the Illustrated London News. So it is, for the early decades at least, an analysis of a particular cross-section of the British public, rather than a survey of American or popular grooming habits.