If you’re thinking of investing in Uber when the company goes public this year, you might want to read the document the company published on Thursday with the Securities and Exchange Commission outlining the potential of its business—and its risks.

Some highlights:

• Uber has grown very, very fast. The company notched 5 billion trips between its 2011 launch and September 2017—and another 5 billion in the subsequent 12 months.

• The total value of Uber’s gross bookings, which counts all the money taken in by all of Uber’s services, a measure of the company’s scale, was $41.5 billion in 2018. More than 80 percent of that is from ridesharing, with most of the rest coming from Uber Eats.

• 91 million people used Uber once a month at the end of 2018.

• Uber’s business model isn’t all there: While there’s optimism about elements of the core business, the company lost more than $3 billion on operations in 2018, revenue growth slowed between Q3 and Q4, and there’s a possibility that the company might continue to offer big incentive payments to drivers for quite some time and never reach profitability.

But one detail in particular caught my eye. About 24 percent of Uber’s bookings—all the money that customers pay through the app and in cash, including driver earnings—occur in just five cities: New York, Los Angeles, San Francisco, London, and São Paulo.

For a company that operates in more than 700 cities, including quite a few giants—Mexico City, Tokyo, Paris, Lagos, Hong Kong, Seoul, and Mumbai, to name a few—that concentration gives Uber a surprising vulnerability at the local level. And they know it. The filing reads:

We experience greater competition in large metropolitan areas than we do in other markets in which we operate, which has led us to offer significant Driver incentives and consumer discounts and promotions in these large metropolitan areas…An economic downturn, increased competition, or regulatory obstacles in any of these key metropolitan areas would adversely affect our business, financial condition, and operating results to a much greater degree than would the occurrence of such events in other areas.

This vulnerability casts a new light on, for example, Uber’s 2015 humiliation of New York City Mayor Bill de Blasio, when the company fought off the City Council’s proposed vehicle cap. That was a warning to other politicians, and a show of power, but it was also a vital business move. The company’s filing also mentions, as a cautionary tale, what happened afterward: Just three years later, the City Council approved minimum rates for drivers and a cap on the number of new ride-hail vehicles. The company also mentions its regulatory challenges in London and San Francisco.

During Uber’s previous skirmishes with cities, I always thought the company’s huge reach and light footprint (very few local employees or inventory) gave them a lot of leverage. They could afford to play hardball with Austin, Texas, one week and San Antonio the next, with little impact on a business distributed so widely.

The filing reveals that certain cities actually have a pretty strong negotiating position. So do the company’s drivers in those places. And its rivals. What appears to be a global, decentralized platform is in fact highly dependent on the whims of a few local politicians, drivers’ groups, and taxi cab unions that can engineer big chokepoints for the company—as London Mayor Sadiq Khan must have done when he revoked the company’s license in 2017. (They got it back last year.)

Another example of the company’s vulnerability by concentration: 15 percent of the bookings pot comes from trips that begin or end at an airport. That might not be so surprising, since airports tend to be cab trips even for car commuters, and being a long way from town, produce high fares. But airports offer a preview of the changing municipal economics that could be coming for Uber. The airport in Charlotte, North Carolina, for example, made more money in 2017 from parking fees than it did from American Airlines. Parking accounted for more than a quarter of the airport’s revenue. As passengers shift to ride-hailing, airport revenues are declining. Airports are an easy place where public authorities can implement a fee on Uber rides to make up for the lost revenue.

That same dynamic is set to play out in cities as well. Congestion pricing, which will soon exist in two of Uber’s biggest markets (New York and London), is just the first way that governments are exerting more fine-grained control over how cities raise money from automobile use.

Uber actually fought for congestion pricing in New York, believing that the one-time fee on private cars entering Manhattan would work in its favor. It probably will. But that’s not the only way street pricing enabled by new technology could work: Cities can tax vehicles per mile traveled, or per hour in the congestion zone, or just slap a huge tax on Uber vehicles because they produce a lot of traffic and serve a relatively wealthy clientele.

One thing the filing makes clear: It wouldn’t take a global movement to stress the company’s business model. A couple big-city mayors could do that all on their own.