Google sent 40% more traffic to publishers in the first week of February 2018 compared to Jan 2017, while Facebook sent approx. 20% less. Of course, this has to do with Facebook's algorithm changes, but also with the growing (and still accelerating) adoption of Google AMP.
Interesting data from Chartbeat for the last 13 months:
Similar numbers from Shareaholic:
Analysis on Digiday with interesting numbers from Popsugar, NBC, TrueAnthem and others: