There appears to be a strong correlation between the number of people using the computer daily and the number of people who run on regular basis because:

a$.$ People who run need to use computers to relax.

b$.$ Using computers causes people to want to run.

c$.$ Both computer use and running have increased during the past few years but one likely doesn't cause the other.

d$.$ Clearly one causes the other but we can't tell which causes which.