Age groupings in polling?

[druidity33]

From a recent poll that is being touted as showing poor "youth" turnout. This youngest age grouping is for 12 years, the middle grouping for 14 years, the third for 19 years and the fourth for an indeterminate amount. How do they devise these groupings? Would the numbers be significantly different if it were 17-32, 33-48, 49-64, 65-80, etc? What percentage of the voting population does each group represent? My 18 yo daughter faced multiple stumbling blocks trying to vote in the primary in MA while attending college in CT. I imagine that affects turnout numbers somehow...


Age 17-29 were 13% of voters: 58% for Sanders v. 21% for Biden
Age 30-44 were 23% of voters: 33% for Sanders v. 30% for Biden
Age 45-64 were 39% of voters: 21% for Sanders v. 51% for Biden
Age 65+ were 25% of voters: 8% for Sanders v. 71% for Biden