Well, Teribus, let's now represent the numbers properly.

1975 referendum: registered voters 40,456,877
2016 referendum: registered voters 46,500,001 (over six million more)

1975 remain vote: 17,368,581
2016 leave vote:    17,410,742
Difference: 2016 leave "wins" (as you said) by 42,161.

But you see, Teribus, there were over SIX MILLION MORE ELECTORS this time round, which makes your 42,161 "lead" look very paltry indeed. In fact, had there been a level playing field for your comparison, I'm sorry to say that this year's leave would have been numerically trounced. In addition, the number of remainers in 1975 was more than double the number of leavers, which makes this year's far more marginal result look a little lean, n'est-ce pas? By the way, I didn't agree that we should have had that referendum either.