Here is a study that says that IQ has gone down in Great Britain over the past 30 years. IQ is always a contentious subject. Most liberals think IQ is meaningless, except when mentioning their own. When I was in high school back in the early 50's, the average IQ in Texas was 102, but now the average is 98. Reasons for the decline are debatable. The Great Britain study gives a few reasons, such as computer games rather than reading and smoking marijuana.

http://www.telegraph.co.uk/education/educationnews/4548943/British-teenagers-have-lower-IQs-than-their-counterparts-did-30-years-ago.html