Jimmy Kimmel's return as Oscars host received an 18.9 rating in Nielsen's overnight numbers from 8-11 p.m. ET, down 15.6 percent from his 2017 debut. Of course, the ABC special ran about 50 minutes after primetime's cutoff, so these numbers are subject to some adjustment.
Last year's Oscars landed a 22.4 rating in Nielsen's overnight numbers, which count 56 metered markets. That was down 4.3 percent from 2016's very preliminary numbers, when Chris Rock hosted.
Rock's turn had already dipped 8 percent from its own predecessor.