While the question is interesting 'do more chasers equate to better /earlier warnings', quantifying this will be nearly impossible as others have noted.
First, what metrics would you use to qualify earlier/ better warning is happening and then how to put it into numbers? TV station issued warnings time? Interview the public on how much warning they got after an event? Damage and casualties vs. warnings? It would be very hard to put together an objective metric to answer the whole question. Also as has been said by others, the definition of chasers is variable, and we all have our chase zones, so the total number of chasers vs. warnings would be tough to get at for any one area.
Also crucial to the question: In the same time as chasers ranks have increased, there have been major technology and policy improvements, such as dual polarization doppler, high resolution satellite, storm simulation and tornado formation studies, push notifications direct to cell phones, better equipped and trained emergency management and response, smarter warning issuance and policy, as well as a very gradual improvement of building codes. New technologies and understanding are probably far more significant than spotter ground truth for improving both warnings, and survivability of severe events. Even climatology might skew the results depending on how we may choose to account for improvements in warnings. While confirming a tornado or severe event, or the damage caused can be helpful for warnings and improving understanding, I rarely see watches or radar indicated warnings be less conservative than report based warnings. A watch or warning almost always exists first regardless of spotters or chasers observations, and should be obeyed by safety conscious public. Sure there is an LEO or public triggered warning that is precautionary when untrained spotters report, but those are not typically improving safety unless they are actually accurate. A tornado warned storm can go from nothing to deadly in moments, so for the public I assume responding to watches and warnings before observations are made to be their main protection. Of course, once a deadly event is unfolding, it does help get a slow/negligent public into action when they see it happening from chaser streams or mass media, etc.
I'd agree the amount of chasers is several hundred anywhere near a big metro with major highways on a moderate or high risk day. Other days there are only a dozen people on remote storms on slight risks with delicate forecasts. In some cases, I would expect the remote slight risk storm day needs the chaser verification much more, and the observation of an event when less expected is more significant to public safety. Also, a low volume of reports is much easier to sort than all the garbage that flows from the circus on a high risk day. I don't envy NOAA offices on these days near OKC or Dallas when the circus is in town. I don't personally chase these days anymore, so there is some self limiting to our population too.
Many chasers think their chasing is important, and the fact is, 98% of it seems purely for enjoyment. Personally I find the ground truth and chasers are essential arguments that you hear many repeat to be way overblown; not totally false, but vastly overestimated. Most of us are just observing for fun and/or getting photos/video. Even a lot of the amateur science done is ridiculous and does not meet with what government and academic researchers state they actually need (this last is knowledge obtained from discussions had with said researchers). I'd say the percent of chasers making a living selling footage (arguably a public need whether for info or entertainment) or doing real science has gone way, way down, as has the average quality/capability of a chaser. Pretty natural conclusion for any population that swells.
Sorry to be so long winded
