I was just checking the latest Standard EuroBarometer, and I found the following chart, which shows some clear correlations...

Younger people are more likely to favour and less likely to oppose EU membership. This suggests it's just a matter of time before a strong European identity develops, but it would be useful to see the same poll 15 years ago to see if the result is more or less constant in time for a given cohort.

More educated people are more likely to favour and less likely to oppose EU membership. One could argue this shows the EU is an elite project.

The more people know about the EU, the more likely they are to favour EU membership and the less likely they are to oppose it. Correlation is not causation.

All of these correlations are monotonic and strong, which should imply significance (though I haven't computed significance levels).

We have met the enemy, and he is us — Pogo