On April 15-16th multiple sources reported seeing an increase in the number of DMARC reports generated or received. Between two and three and a half times as many reports per day were observed, depending on the source. There was some hope there would be a public announcement during the RSA Conference in San Francisco last week to explain this increase, but so far no such announcement has come to light.
The dmarcian.com service shares the number and source of DMARC reports being processed each day at this URL. A peak of just under 53,000 reports was observed for April 15, compared to an average before the spike of about 15,500 reports per day. Twelve days after that peak, reporting levels may be dropping but remain elevated at roughly 28,000. The end of a plateau in reporting activity from Tuesday, April 21 at 44,558 reports is still visible at the time of this writing.
If you are aware of other public sources for this kind of statistic, please let us know. A public explanation for the increased level of DMARC reporting is still being sought.