A taxi medallion, also known as a CPNC (Certificate of Public Necessity and Convenience), is a transferable permit in the United States allowing a taxicab to operate. Several major cities in the US use these in their taxi licensing systems, including New York City, Boston, Chicago, Philadelphia, and San Francisco.
The medallion system is a government-created intentional constraint on the supply of taxicabs, and because cities have historically increased the number of medallions at a slower rate than the growth in demand for taxis, medallions have generally been considered a valuable investment,[1][2] though recently the increased supply of cars for hire created by ridesharing companies has been eroding the value of medallions.[3][4][5]
...the taxi medallion system, a regulatory scheme in which the right to operate a taxi is thoroughly divorced from the actual work of driving one... When New York City first issued taxi medallions in 1937, they were just licenses, worth $150 in today's terms. ... In New York, Chicago, and Boston, the number of medallions has barely budged since they were issued in the 1930s. New York went 60 years without issuing new medallions, and it's only been a trickle since. ... New York's tight limits on the number of medallions in circulation has suppressed the supply of cabs. There are 13,237 medallions now outstanding, a few hundred fewer than in 1937, but a huge supply of drivers competing to lease them.
...after the stock market crash in 1929, job seekers swelled the ranks of New York City cabdrivers to 30,000 in 1930. ...too many cabs were chasing too few passengers in the Depression years. "The Haas Act tried to remedy that problem by stopping the issuance of any new vehicle licenses."