The idea behind the concept of generations is that people born at a certain time share similar experiences, which in turn shape common attitudes.
The “Greatest” and “Silent” generations, born in the early decades of the 20th century, witnessed economic adversity and global conflict, going on to form relatively leftwing views. Baby boomers grew up accustomed to growth and prosperity, and went on to lean strongly conservative.
It was a similar story for millennials, who entered adulthood in the aftermath of the global financial crisis to be greeted by high unemployment, anaemic income growth, and ballooning house price to income ratios, going on to champion strongly progressive politics.