The Pew Research Center asked people if they agreed with the statement “I never doubt the existence of God.”
You want to see that number low because it means more people have doubts (or don’t believe in god altogether).
This is what they found — and it’s incredible:

Wow. Look at the line for Millennials. It’s dropping. Quickly.
The difference between the youngest and oldest generations has gone from a 6 point gap in 2007 to a 21 point gap now.
Unshakable religious belief is not as strong as it used to be. That’s a good sign. It’s a trend that needs to continue.
If you’d like to see how that question was answered by different demographics, you can do so here.
(Thanks to Daniel for the link!)