How difficult is it to steel a car?

Steeling cars was much simpler before engine immobilizers were introduced. Some of the most common cars stolen were Mazda 323, 626 and The Ford badged Japanese cars.
These cars were easy to steal because bypassing the locking system was easy. The cars were basic (no computers) and information on stealing them was easy to come by.
Even if you couldn't bypass the locking system getting the engine to run wasn't that hard. All you needed was Fuel, Spark, and power to the starter motor. This was not hard and it was what was commonly known as 'Hot-wiring a car'.
Somewhere around 1996/97 most car manufacturers started to include an engine immobilizer in their cars. The Mazda 323,626, etc also recieved an engine immobilizer. After the engine immobilizer was fitted in the Mazda the number of thefts of these vehicles (and most immobilized cars) dropped dramatically. Hot-wiring a car became quite complicated. The Mazda 323 for example had the immobilizer integrated into the car's ECU. The ECU controls all the engines electrical processes, including Fuel & Spark. So in order to hot-wire a Mazda 323 you had to bypass the ECU or Hack the ECU.
The average car thief dosent want to be hanging around for very long rewiring a car or hacking a car's security computer/wiring. Also the average car thief isn't that smart. If you were that smart why would you steal a 323 in the first place, and if you were really that smart why would you be stealing cars at all?
While many early model immobilized cars require a high degree of information and time to hack the security systems there are many cars that are vulnerable to hacking methods.
I am not sure on the real statistics of cars being stolen, but there is an underlying problem that exists with all security systems. The problem is that if you have enough time to work out a process of how to bypass, hack, pick the lock on a particular model of car, then that process would work on every car of the same model, due to the fact that they are mass produced and all exactly the same.
To sum up most modern cars are more secure due to the introduction of immobilizer systems. There are some cars that have easily exploitable flaws and could be stolen very quickly. Just watch a locksmith. Hopefully it will take the thieves more time and expense to learn the art of bypassing these security systems.