Google Page Rank of my Blog

Google has decreased my Blog's Pagerank recently. It was 3 earlier but now my page rank is only 2. Any idea?
Is it due to the fact that I was using from blogspot earlier and now I am using it for my self hosted wordpress blog! Page Rank 3 was when my blog hosted on blogspot. Google may think about my site and decide in next page rank update for my Page rank.

Page Rank is just one of the parameters Google consider for websites value. It has lots of parameters. You can see my Alexa rank has increased. It is now 160,000. Traffic has also increased from Google despite decrease in Page Rank.