Lots of political slogans turn out to be bollocks, but New Labour's "Things Can Only Get Better" ended up being worse than most. Taken from the song that John Prescott danced to on that famous election night in 1997, it summed up the naïve optimism of the post-Britpop era, when 18 years of Tory rule gave way to an age of Tony Blair and the Spice Girls and AOL chat rooms. But the Spice Girls split up. Princess Diana died. 9/11 happened. We went to war in Afghanistan, then Iraq. There was too much awful news for Trevor McDonald to handle in one bulletin, so 24-hour news was invented. Now we could stay up all night watching the world burn and heroes die: 7/7, the Coalition, Brexit, 2016, Trump. All that bad news led to a surplus of anger, fear and rage, so we invented social media as an outlet. It was finally acceptable to scream "Tory cunt!" at random strangers. Now that's pretty much all we do: watch, hate, react. So what happened to all that optimism? What happened to the generation of voters who put New Labour in power? Well, they're probably voting Conservative now. For 20 years, pollsters Ipsos MORI have been reporting on "How Britain Voted" after each election, using thousands of interviews to figure out which groups turned out for which parties. When Tony Blair annihilated the Tories back in 1997 he won in every age group, but his biggest lead was with young people. He won 18 to 24-year-olds by 22 percentage points, 25 to 34-year-olds by 21 points and 35 to 44-year-olds by 20 points. In 2005, those bright young 18 to 44-year-olds were now grizzled old 26 to 52-year-olds. Looking at the same Ipsos MORI data for that year, 25 to 34-year-olds went Labour by 13 points, 35 to 44-year-olds by 14 points and 45 to 54-year-olds by only four points. It's still a lead, and the age breakdown doesn't match exactly after eight years, but the lead isn't as big as it was. Still, that's after eight years of Labour government and a war in Iraq. It's not surprising that Labour were less popular than they had been, and the fall in popularity is consistent across age groups – even the shiny new 18 to 24-year-olds only backed Labour by ten points. What happens, though, if we fast forward another ten years, to the 2015 election after five years of Coalition rule? The young hopefuls from 1997 are now creaking and elderly 36 to 62-year-olds. The new 18 to 24-year-olds are solidly Labour again, with Miliband leading them by 16 points over the Tories, but 35 to 44-year-olds are a dead heat, 45 to 54-year-olds lean Tory by three points, and 55 to 64-year-olds give the Tories a six-point lead. What happened? There are several possible answers, and to be honest it's hard to pull them apart. It could be that people naturally get more Conservative as they get older. Brains age, and this has some effect on our personality. We become more mature, more experienced and better adjusted at dealing with our emotions, but we also slow down a little and become less open to change and new experiences. That could explain why the world seems increasingly split between young, open liberal people and old, closed conservatives. It's a tempting theory, but it's hard to prove – after all, even over-65s were happy to ditch the Tories in 1997 and vote Labour. There are many reasons why voters change their minds, too. Did Labour supporters switch sides because they got old, or did they switch because they got fed up with the guy they voted for and wanted to shake things up again? There's a third possibility, too – maybe they didn't change their minds that much. Even back in 1997, only about half of 18 to 24-year-olds showed up to vote, with voter turnout getting much higher with age. People tend to assume that the rest would vote the same way if only they got to the polling booths, but is a Labour "supporter" who doesn't bother to vote still a Labour supporter? It could just be that, as a generation gets older, and more people turn out to vote, we get a truer idea of their real views. Whatever the reason, probably the most important thing is that people do change. We're into the seventh year of a Tory government that will probably carry on for at least another five. Brexit was delivered largely on the backs of old, right-wing people. Many on the left are understandably looking at the left-wing youth of today and imagining that, in another 20 years, we'll see decades of uninterrupted Labour rule. The truth is it doesn't work like that. We aren't Labour or Tory for life. So if you want to get more people voting Labour, you need to get out and start persuading them now.