Although this is a practical application of Kimono Labs (except for the APIs for CrunchBase and Twitter, which have their
own APIs that are more reliable), there really isn't much to this visualization other than comparing S14 and W14, which is not enough to establish any causal trends. the visualization doesn't indicate any major shifts either. YC invests in a wider variety of companies in the later years, yes, but there isn't an constant increase or decrease in a particular category.
Additionally, how did you categorize each YC startup? I checked your APIs and I didn't see that data in any of them.