Millennials are shattering the oldest rule in politics

“If you are not a liberal at 25, you have no heart. If you are not a conservative at 35 you have no brain.” So said Winston Churchill. Or US president John Adams. Or perhaps King Oscar II of Sweden. Variations of this aphorism have circulated since the 18th century, underscoring the well-established rule that as people grow older, they tend to become more conservative.

The pattern has held remarkably firm. By my calculations, members of Britain’s “silent generation”, born between 1928 and 1945, were five percentage points less conservative than the national average at age 35, but around five points more conservative by age 70. The “baby boomer” generation traced the same path, and “Gen X”, born between 1965 and 1980, are now following suit.

Millennials — born between 1981 and 1996 — started out on the same trajectory, but then something changed. The shift has striking implications for the UK’s Conservatives and US Republicans, who can no longer simply rely on their base being replenished as the years pass.

It’s not every day that concepts from public health analytics find a use in politics, but if you’re a strategist on the right, then now might be a good time for a primer on untangling age, period and cohort effects. Age effects are changes that happen over someone’s life regardless of when they are born, period effects result from events that affect all ages simultaneously, and cohort effects stem from differences that emerge among people who experience a common event at the same time.

This framework is used to understand differences in a population and whether they are likely to be lasting. This makes it perfectly suited to interrogating why support for conservative parties is so low among millennials and whether it will stay there.

Let’s start with age effects, and the oldest rule in politics: people become more conservative with age. If millennials’ liberal inclinations are merely a result of this age effect, then at age 35 they too should be around five points less conservative than the national average, and can be relied upon to gradually become more conservative. In fact, they’re more like 15 points less conservative, and in both Britain and the US are by far the least conservative 35-year-olds in recorded history.

On to period effects. Could some force be pushing voters of all ages away from the right? In the UK there has certainly been an event. Support for the Tories plummeted across all ages during Liz Truss’s brief tenure, and has only partially rebounded. But a population-wide effect cannot completely explain millennials’ liberal exceptionalism, nor why we see the same pattern in the US without the same shock.

So the most likely explanation is a cohort effect — that millennials have developed different values to previous generations, shaped by experiences unique to them, and they do not feel conservatives share these.

This is borne out by US survey data showing that, having reached political maturity in the aftermath of the global financial crisis, millennials are tacking much further to the left on economics than previous generations did, favouring greater redistribution from rich to poor.

Similar patterns are evident in Britain, where millennials are more economically leftwing than Gen-Xers and boomers were at the same age, and Brexit has alienated a higher share of former Tory backers among this generation than any other. Even before Truss, two-thirds of millennials who had backed the Conservatives before the EU referendum were no longer planning to vote for the party again, and one in four said they now strongly disliked the Tories.

The data is clear that millennials are not simply going to age into conservatism. To reverse a cohort effect, you have to do something for that cohort. Home ownership continues to prove more elusive for millennials than for earlier generations at the same age in both countries. With houses increasingly difficult to afford, a good place to start would be to help more millennials get on to the housing ladder. Serious proposals for reforming two of the world’s most expensive childcare systems would be another.

UK millennials and their “Gen Z” younger cousins will probably cast more votes than boomers in the next general election. After years of being considered an electoral afterthought, their vote will soon be pivotal. Without drastic changes to both policy and messaging, that could consign conservative parties to an increasingly distant second place.

[email protected], @jburnmurdoch