Above: Face With Tears of Joy was the most used emoji on iOS in 2017. Image: Apple.
Above: Comparison of Tears of Joy and ROFL on Emojipedia in years 2015-2018. Image: Emojipedia.
What we see is a steady increase in use of this emoji until 2017, when a sharp decline hit. While the ROFL character took the slack for some of this use, we still see less views of both laughing emojis combined in 2018 than we have for over two years.
Note: Without “one true source” of emoji data, there isn't a foolproof way to determine which emojis as used how often. Emojipedia page view data tends to track fairly closely to usage on public platforms such as Facebook and Twitter, and as such seems a reasonable method of determining popularity over time. ↩︎