Even in 2010 and 20111, with the exception of the top end of the market, housing prices didn't really drop that much, largely because sellers held rather than selling. So it shows no such thing.
I know that the plural of anecdote is not data, but my experience in the middle of the Bay Area doesn't fit at all your rosy narrative. The value of my home dropped by about 20% (as assessed by the bank when I tried to refinance), while the County acknowledged 5% drop; of course, when the market rebounded, the County was very quick to get back to the original trend of keeping increasing the tax base like nothing happened.
Even most conservatives in California think that granting businesses Prop 13 protection was a mistake. The ads you see pushing back against this change are mostly funded by companies that own lots of real estate. When the total property tax bill paid by residents has grown from being about the same as the total commercial property tax bill in 1970 to being a whopping 2.4x as much now (because of companies holding and leasing rather than selling), and when those savings are mostly going into the pockets of stockholders outside the state of California, it's pretty clear that the "leg" you're talking about is screwing California taxpayers.
Again, the only time when a fair assessment can be made about the value of a property is when it's sold. Everything else is arbitrary. I don't watch ads, but I'm looking at who is pushing for Prop15: realtors and government people who can't wait to get their hands on a huge windfall to piss it in the wind with their pet projects. I am sure that they're pushing this just to right a wrong, no self-serving interests in it, no Sir!
What would be the impact on the companies affected? that is mentioned nowhere in the Voter's pamphlet I received, only how much money can be extracted. Pure greed.
Even with Prop 15, Prop 13 still won't be fair to newcomers, and it will still be a major contributor to traffic problems, but at least businesses won't be getting away with not paying their fair share of the tax revenue that pays for our schools. Vote YES on Prop 15. Your kids and grandkids will thank you.
Yeah, like the little bone thrown at us with Prop19. That bone is small and rotten, who wouldn't want to let their kids have that?