I'll tell you what I don't understand.
How did the polls get it so wrong and in the light of that how can we know that the majority of leave voters were old?
the polls didn't get it so wrong (some got it right)
i wrote the following elsewhere last week.....
"Brexit polling was all over the place. In particular, there was a divide between polls conducted over the telephone and online. As it turned out the online polls in this referendum were the only piece of information informing the world of the correct risk of a Brexit throughout the campaign. The online polls showed the race very close within a margin of error either side of 50/50, with a slight advantage for the Leave campaign. Throughout the campaign the telephone polls showed Remain comfortably ahead before showing an average 2.7% Remain lead over the final four weeks. The online polls showed Leave ahead more often than Remain, with an average lead for Leave of 1.8% over the same period. In total over the campaign period, 78% of the telephone polls showed a Remain lead, whilst 63% of the online polls showed Leave ahead"
"Seven polling companies issued ‘final’ polls of voting intentions in the EU referendum. While no company forecast the eventual result exactly, in three cases the result was within the poll’s margin of error of +/- 3%. In one case Leave were correctly estimated to be ahead. In the four remaining cases, however, support for Remain was clearly overestimated. This is obviously a disappointing result for the pollsters because every single poll, even those within sampling error, overstated the Remain vote share."