What is a third variable condition that could create the following correlation?

The popularity of online job portals is correlated to the number of people changing jobs.

Question

What is a third variable condition that could create the following correlation?

The popularity of online job portals is correlated to the number of people changing jobs.

anonymous · Answer

internet connectivity
peer pressure
lots of available jobs
health benefits
availability of better technology

destinymasha · Answer

variable - something liable to change 
that being said, i would think  C lots of available jobs 
~there's not always going to be available jobs - but neither internet connectivity?