Source: Uber.

Over the past year, there's been a major shift in the vehicle-for-hire market. Once marked by luxury-car services for high-end users, taxis for the hoi polloi, and rental cars for multi-day business trips, ride-sharing services such as Uber and Lyft have quickly grown at the expense of these other ground-transportation providers.

It's been an acrimonious relationship to say the least. In Paris, taxi drivers blocked Uber drivers, vandalized vehicles with metal bats, and started fires. In the U.S., things have been less violent but just as acrimonious, as taxicab-funded NYC Mayor Bill de Blasio unsuccessfully attempted to limit Uber's growth in the city. And this is not a one-party issue: Last year, Republicans in Philadelphia's Parking Authority, a state agency, sought to ban the service.

A key reason Uber and Lyft are stealing market share is they're cheaper. Source: Certify.

To be fair to these entrenched agencies, ride-sharing is a clear threat to their business models. In the minds of many, the question is not if, but when, ride-sharing services will eclipse these players in total market share. As an example of how value-destructive ride-sharing services have been to taxis, medallion financier Medallion Financial has struggled as the value of medallions, a previously lucrative investment, are starting to fall below their purchase price. According to travel and expense management software provider Certify, ride-sharing companies have already eclipsed taxis in the key business-traveler demographic.

Certify shows a clear trend
When it comes to the all-important business traveler, ride sharing has tremendously increased in scale, growing from 8% of all ground transportation in the first quarter of 2014 to 34% in the recently completed third calendar quarter of 2015. Here's a visual representation of ride-sharing growth:

Data source: Certify.

There's a clear trend in market-share growth for ride-sharing services. After tying taxis in the first quarter of this year, ride-sharing services continue to grow mostly at the expense of taxicabs. For the latter, its share of the business-traveler set has noticeably decreased, losing 15 percentage points during the same time frame. Even the high-end rental-car market is not immune, as ride-sharing services, including Uber Black, have cut into its market share as well. 

Will Uber eclipse $100 billion?
Many predict that Uber is on a glide path to becoming a $100 billion company. At Uber's last funding round at the end of July, the company raised $1 billion from a group of investors, including Microsoft, at a valuation of $51 billion. Uber finds itself in good company: The only other venture-capital-backed start-up that surpassed $50 billion was Facebook -- and Uber accomplished the goal two years faster than the social-media behemoth.

In a recent article, NYU finance professor and valuation guru Aswath Damodaran upgraded his valuation of the company from $5.9 billion in June 2014 to $23.4 billion, mostly based on total market and growth figures that were larger than previously expected. And if Boston and San Francisco are Uber's future, as in those cities ride sharing is the No. 1 choice for business travelers, the market could be even larger than Damodaran expects.

In addition, recently Uber announced its intentions to pair with small business to capitalize on its logistical advantage with UberRUSH for deliveries, opening up a new market for Uber drivers. In the end, the $100 billion figure could be laughably inadequate, and although the company isn't public, investors should watch Uber's effects on both tangential and competing businesses.

Jamal Carnette has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Facebook. The Motley Fool owns shares of Microsoft. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.