Strangely enough I've heard far more people make this "joke" than actual vegans speaking up. Even when living in LA.
Still, I'm not sure if it's a big factor. You likely know who is vegan in your circles, because veganism is unusual enough to be a good topic for gossip, you can easily see it when sharing a meal with someone, and it's also something you'd like to know when inviting people over, if you want to be a good host. So I think a more relevant estimate would be number of vegans you know vs. how many of them announce their veganism at the earliest opportunity.
The later group used to be larger, but I don't remember anybody doing that recently.
There are more Americans with gambling addictions than there are people committed to vegan diets!”
Chart: https://x.com/cremieuxrecueil/status/1805367282270433791?s=4...