Marathon times

I have been keeping track of the 10 K we walk every year. It must be said that I amble well. And that I don't run.

Marathon time when my son had to walk with me. (2003)
Me: 2:25:50
Son: 2:25:50
Marathon time when he was allowed to partially walk on his own. (2004)
Me: 2:30:45
Son: 2:13:25
Marathon time when he walked on his own (2005)
Me: 2:26:59
Son: 1:48:06

Do we see a pattern here?