In the UK they call a car's liscence plate a 'number plate' and they are a big business.
Normal number plates are issued to a new car when it is registered by the car dealer with the DVLA and they tend to stay with the car for its entire 'life'.
The front plate here in the UK is white and the rear one is bright yellow but that varies from country to country around Europe. The thing that is totally unique about UK plates is that the two numbers you see in the photo above indicate the year that the car is manufactured. So the 51 you see in the example above tells you that the car was made between September 1st, 2001 to February 29th 2002 and the plates issued by the DVLA from March 1st 2002 would have had an 02.
The impact of this on an economic level is that people desire to have the latest number plate and tend to upgrade their car just for that reason. As for used cars then you could have the same car with the same mileage and even made in the same year yet one has an 07 plate and the other a 57 plate and the 57 plated car would be worth more on the market.
There is also custom plates that you can pay for from the DVLA and they remain the property of the individual. Desire your initials? How about a nickname? Well there are two ways to get it. First you can hope that no one has ordered it already from the DVLA and pay about £250 for it OR if you are not so fortunate you will have to try to buy it off of the individual who already owns it.
In the case of the above plate, which belongs to footballer Cristiano Ronaldo's Bentley you would probably have to pay him millions of dollars or pounds to get him to sell that to you. You up for it?