Between 1997 and 2007,mobile Cell Phone Subscriptions Have Steadily Increased

Between 1997 and 2007,mobile cell phone subscriptions have steadily increased from 18 users per 100 inhabitants to roughly 97 users per 100 inhabitants in developed countries.During this same time,diagnosed cases of autism have also steadily increased from around 50,000 to 250,000.Your friend decides that cell phones must cause autism.Briefly describe what your response would be to your friend's conclusion,indicating any possible relationship(s)that may or may not exist.