Here's one summary of it as of last year:
> The infamous "Twitter tax break" provided by former Mayor Ed Lee to lure companies, including Twitter, to mid-Market by exempting them from a portion of their payroll taxes, had its sunset in 2019. Many argued that it did little to revitalize mid-Market — and certainly Twitter former fancy cafeteria didn't help in terms of workers spending money at local businesses — and it just ended up costing the city about $10 million a year in lost revenue. > https://sfist.com/2023/02/09/mayor-london-breed-announces-ta...
When the Twitter tax break expired in 2019, the Chronicle also did a pretty thorough survey of the mixed effects: https://projects.sfchronicle.com/2019/mid-market/