What is the Most Popular Car?

I was walking on the street, and I noticed something. On every street I walked passed, I saw a VW Golf. So, in my complex brain, I began to wonder. If I have seen a golf on every street  I walked passed, does that mean that the VW Golf is the most common car type. I decided to collect more data. I walked pass another 10 streets. Guess what I noticed, on all of these streets I saw at least one VW Golf. It was the most common car I saw. So, when I got home, I decided to do a quick and simple GOOGLE search on the subject. According to Top Gear, the most common car of 2010 was the Ford Fiesta, however I soon realised that Top Gear's figure was based on Sales. Therefore, my question is still unanswered. Can you answer this question for me?