Steven Hayward, the numbers guy at Power Line, posts this chart showing the caucus preferences by age bracket. I'd call your attention to the differences in both candidate choice and propensity to caucus by age groups.
I find particularly interesting that 78% of those attending a caucus were 45 or older, and that an actual majority of these chose Trump. He also won a plurality of the 30-44 group, though not an absolute majority. It appears most young Iowans have things other than politics on their minds and stayed home.
