There was an unprecedent 4% swing in the polls from two weeks before the poll to the results on the day. The last full referendum on the EU wa in 1975, and the locals are used to tactical voting at every other government level, up to and including a General (i.e. Prime Ministerial) Election. My direct family all voted in. Most (but not all) of my sister's family were in/remain as well. There's a 60+ year age spread in that cohort alone, only two of whom were old enough to vote last time around. The biggest single factor on the day was probably that it pissed down with rain all day across most of the South East, including London, where a large fraction of the population lives. This skews heavily against the young and the (legal) immigrants, who may have multiple jobs, and the elderly, who struggle with public transport. My borough voted remain by nearly 70%, my Dad's voted out by similar margins. The U.K. of Great Britain and Northern Ireland would comfortably fit inside California, yet has (roughly) one fifth the population of the U.S. The politics of these little islands are far more complex than those in the U.S., and some of the laws in our (unwritten) constitution are just as arcane and stupid as those anywhere in the world. America got to start afresh in 1776 and keep only the good bits (and some bad bits). At least we don't deliberately rig things so that black people have to take a whole day off work to vote.