According to the researchers' standard model, which requires a minimum of 47 soldiers per 1,000 citizens for a country to survive if the dead were to rise, only North Korea, which has 47.4 military personnel per 1,000 residents, has any sort of chance of surviving a zombie outbreak.
Stressing that an ordinary human vs. zombie confrontation mostly simply leads to humanity's annihilation, the mathematicians calculated that by adding the parameter of firearms' trained military personnel to fight the undead, our chances improve. In fact, according to their analysis, "the initial amount of military personnel play a key [role in] our survival, even when the zombies are extremely aggressive" and have a "large [numerical] advantage."
On that basis, they concluded that "be it for North Korea or for other countries like the United States (4.2 active military per 1000) or Brazil (1.6 active military per 1000), the best strategy to save mankind suggested by our model is to invest in their own populace, making their standard humans more healthy and more capable to survive." Accordingly, for ordinary people, the academics suggested watching one's diet, engaging in sports and physical exercise, and taking courses in self-defense.
Admitting that their scenario is far-fetched and that zombies are fictional, the researchers nevertheless argued that "even if a zombie apocalypse turns out to be something that only happens in [the movies and video games], learning how to mathematically model this kind of scenario can be very useful, as we can observe relations like this in many other fields of research, such as economy, biology, and social behavior."