Here is the most information on the population of Jat in India and Western UP
http://www.hindustantimes.com/India-...e1-797307.aspx
As per the link above The Jat population in India is believed to be around 8.25 crore. In UP, the caste comprises less than 6% of population but their dense presence in the state’s western part affects more than 50 assembly seats.
Thanks
Sanjeev