Basically it would involve going through the previous batches and manually labelling them. I might pick a couple of other classes to do it for, but it's probably too much work to do it for all of them.
"... which suggests YC is still open to funding consumer startups that have the potential to be massmarket without a clear revenue stream"
Nice way of looking at the data but it's difficult to draw conclusions like the above. There are always posts that describe how people changed course partway through or even changed at the last minute. YC can't know how things are likely to go at the time they make the offers.
It would be interesting to compare YC startups considering also their income so we can see not only chosen business models but also how much they earn.
It would be fascinating to see a trendline across batches - do you feel you'd have the data to do that?