A statistical model, from Yair Ghitza of Catalist and Andrew Gelman of Columbia University, estimates when people form their political preferences. The analysis uses presidential approval ratings from Gallup to approximate political events "that estimates when people form their political preferences."
Amanda Cox for the Upshot demonstrates the model in an interactive. Simply drag the slider to see how the political leanings of you and your birth cohort changed over time. The takeaway: Events between the ages of 18 to 24 are far more influential than those that occur at an older age.
It seems like the model might apply to a lot of things in life.