It would be cool to see how many of the IDs made this past year were applied to previous years. That could be shown by year or by broad categories of life. For example, you could see how much the needs ID pile for 2018 went down in 2021, or how much the Arachnid needs ID pile for all years before 2021 went down in 2021.
Using the Growth stats as a model, you could reverse it and show the start of the year with the number of observations prior to 2021 needing ID and then show over the course of 2021 how that number went down. Maybe better than that, show categories of casual, needs ID, and research grade as percents of the total to see how those changed over the year.
I definitely agree there should be more statistics related to identification to show how much progress has been made by the many identifiers. I’m especially curious about the progress made on the observations needing ID from previous years. By showing broad statistics for all of iNaturalist there is no issue of gamification.