Logan's Run (1976) - dir. Michael Anderson
Logan's Run starts with a fantastic premise - the human population now lives in a small group of cities, and everyone is ritually executed when they reach a certain age. But in one particular way, Logan's Run models human behavior in real-life dystopia better than many of its more prestigious counterparts.
In the large majority of fictional dystopian societies, freethinkers are a tiny minority. The sheeplike masses comply with the dictator's commands, and don't even think to ask 'why?' Dissent is literally unthinkable.
Life is a bit different in Logan's Run. Rarely a minute goes by without someone trying to escape. Although, as in 1984 and Fahrenheit 451, our hero meets a woman who introduces him to a secret society of rebels, individual action against the state is ubiquitous enough to make the job of catching them a full-time job.
Few of these runners, even the organized ones, seem to be politically motivated. Most of them simply don't want to die. Even Jessica, our heroine, is perfectly ready to give up rebellion in order to live with Logan.
It is ironic that the same instinct for self-preservation that kept this totalitarian system is also the primary impetuous for leaving it. But I suppose it is a mirror to its real-life counterparts.
Likewise, mass suicide is very, very rare in the real world. And then, it is usually out of fear of torture or other desperation rather than the altruistic cult ceremony we see in the film. (Jonestown and Heaven's Gate stand out because of their rarity)
So, even with the intense societal and religious pressure, it makes perfect sense for so many runners to emerge. The ratio seems more or less consistent with what we saw in Nazi Germany and Soviet Russia.
Logan's Run is the 19th entry in my 45.1 Essential Dystopias list.