Age comparison between the monuments

Is there any difference in age to perform in the monuments? This barchart shows the average age of the top-10 finishers for the last 20 years in the 5 monuments. In Flanders, Lombardia and Liege-Bastogne-Liege the average age is around 29.5. In Paris-Roubaix the average age is significant higher with 30.1. Milano-SanRemo, the longest in distance, has the lowest average age with 28.7.