This sort of measure seems shortsighted, because it would bias itself very strongly against large companies which employ unskilled workers.
The larger a company gets, the more responsibility its leadership needs. The more responsibility you have within a company, the better you're paid. However, unskilled workers tend to earn near minimum wage no matter what, because they have little to no responsibility within the company; they're don't need to make any sort of company-impacting decisions or judgements.
Given that situation, it seems like this would be the sort of law which would punish companies for growing too large while still employing unskilled workers. Perversely, it would reward companies which employ mostly skilled or academic workers - like those found in tech companies. Each of those workers wields proportionally more responsibility in their organization, so the gap is not so large.
Worse, it completely ignores the reality of how companies operate. CEO's aren't even always paid a salary; see the $1 salary. en.wikipedia.org/wiki/One-dollar_salary . This sort of measure would only encourage bypassing it by funding their leadership with bonuses or stock or assets, instead of direct payment.
Finally, who is to say that this doesn't just increase the (already ridiculous) cost of doing business in California? Does anyone seriously think that a company wouldn't pass the tax on to its customers? Only the most monolithic companies could afford not to.
I understand the idea behind this misguided bill, it's trying to get more people into the middle class. But instead, it looks more like it would give fewer options for those looking to move up - if it even does anything at all.