As many as one would like to substantiate a claim of IRC being "alive" or "dead"? I am fairly certain that the majority of the users I see are alive and real, but how am I even supposed to prove that?
Proving 'aliveness' would be indeed difficult, the more time passes, the harder.
It depends on the network, taking one of the oldest, still existing, EFNET for example, has many bots for technical reasons, so some channel can't be taken over in case of netsplits. The ratio seems like up to a handful of users vs. a dozen bots for the smaller channels. That alone should distort the numbers massively.
For other networks, let's say LiberaChat, it may look different from a technical point of view, but there arises the question of 'philosophical zombiness', as I've witnessed the same shitheadedness repeating the same nonsense over periods of years, when I made the mistake to go there again. That could be bots, now even more so, or just philosophical zombies. Or some so called neurodiversity in action, which I couldn't care less about.
Does it matter? Probably not. It could be seen as a failure of my Zen, messing up my own solipsistic creation ;)