Political science has long sought to understand how citizens form their political identities, values and behaviours. However, robust causal evidence on how policy interventions can shape the political socialisation process remains limited. The three papers that make up this thesis investigate how citizens – and young citizens in particular – change their political attitudes and behaviours in response to large-scale policy interventions, specifically: income transparency, enfranchisement and compulsory voting. In the first paper, I take advantage of a quasi-experiment in Finland to study whether income transparency – the public release of citizens’ income information – affects support for redistribution. Using survey data and a before-and-after research design, I show that income transparency leaves public support for redistribution largely unchanged, but that young people increase their support for redistribution in response to the intervention. This suggests that redistributive preferences are rooted in more stable, underlying ideologies, that are difficult to alter once they are formed in early adulthood. In the second paper, I leverage a quasi-experiment in Germany to study whether enfranchisement improves citizens’ political maturity. Using survey data and a difference-indifferences approach, I show that enfranchising 16-year-olds can equalise prior differences in political maturity between underage and adult youth. This suggests that political maturity should be understood not just as a precondition, but also as an outcome of the right to vote. In the third paper, I take advantage of a quasi-experiment in Brazil to investigate whether compulsory voting instils voting habits in young people. Using administrative data and a regression discontinuity design, I show that voting fails to be habit-forming when it is compulsory. This finding clarifies the scope conditions of prior research on voting habits, as it runs counter to available evidence from voluntary voting systems.