The number of drivers for transportation network companies Uber and Lyft who operate in the companies' hometown of San Francisco might vary wildly from month to month, or even from Saturday night to Monday morning. While that's partly the premise of the ride-hailing technology industry, the Treasurer's Office has expressed a vested interested in pinning down that number as it demands individual drivers obtain business licenses to work within the city.

That process began in April when City Treasurer Jose Cisneros sent out 37,000 letters to a list of drivers provided by Uber and Lyft, asking them to apply for business licenses that cost $91 per year or else face penalties for operating without one ($155 per year). But in June, presumably prompted by a lack of registrants, Cisneros forgave fines and extended the deadline for business license registration to August.

These days, according to numbers the Treasurer's Office shared with the Examiner, there may be as many as 45,000 Uber and Lyft drivers who operate in San Francisco, dwarfing the 1,800 or so medallion-equipped taxis on our streets. 12,000 or so people responded to the first batch of 37,000 forms sent out by the Treasurer's Office to say that they were no longer driving for Uber and/or Lyft in San Francisco, had already registered for a business license, or considered themselves employees of the companies (a sentiment not shared by Uber and Lyft, who insist their drivers are contractors and no more).

On the other hand, 20,000 drivers have registered since notices were sent out, providing a rough baseline number of Uber and Lyft drivers. Yet an added 20,000 notices have since been sent to another group of potential drivers according to Amanda Kahn Fried of the Treasurer's Office. Adding the original 37,000 letters and the new set of 20,000 while subtracting the 12,000 respondents who said they weren't driving for Uber/Lyft, the Examiner estimates 45,000 active or Uber and Lyft drivers.

Or, more specifically, it calls them "not yet discounted" — Uber and Lyft drivers until proven otherwise, essentially. Those murky numbers best represent a broad effort from the Treasurer's Office to obtain as many Business License registrants as possible. How many Uber and Lyft drivers are out and about in San Francisco right now? The answer, for now, is blowin' in the wind.

Previously: Treasurer Gives Uber And Lyft Drivers Longer To Obtain Business Licenses, Forgives Fines

SF's 37,000 Lyft and Uber Drivers Will Be Ordered To Get Business Licenses