I was comparing the paces from my three fastest marathons and I noticed a trend:
In all three marathons there was a consistent increase in pace per mile starting right after mile 15:During all three marathons, between miles 16 and 24, my speed gradually got slower until mile 24. At mile 24 I start to "kick" and use up any energy reserves, hence the faster paces for 24 through 26.2. This chart shows that I always seem to start slightly sucking wind at right around mile 16. This is the point where my race should actually start, however in each case I started to slowly to lose ground.
I'm not quite "hitting the wall" at mile 16, but this upward trajectory is a tell-tale indicator that I need to figure out how to stay strong through mile 24 when my kick starts. I am guessing one thing I need to NOT do is to increase my speed dramatically after mile 13, which is what I think I have done in the past (consciously or unconsciously).