Studies show that 26% of the population bite their nails, in other words almost 3 out of 10 people. Among young adults between the ages of 21 and 25 it is as high as 42%. In other words, you are certainly not alone if you want to kick the habit.
(source: Ipsos research with 1000 respondents: Nail biting - Survey in France (representative for Europe), iOmnibus research - November 2014. Prepared for Oystershell).