Chatter Plots: StarCraft 2 Unit Survival Rates
How long does the average Marine live?
What proportion of Oracles survive until the end of a game?
To answer these questions and more, we plotted the life expectancies of SC2 army units, drawing from a replay-based dataset including a number of major tournaments in the latter portion of 2019 (Asus ROG, Blizzcon, Cheesadelphia, HomeStory Cup XX, Nation Wars, Qlash Invitational, and WCS Fall).
We used the Kaplan-Meier estimator to calculate survival rates, a metric typically used in bio-statistics. Kaplan-Meier accounts for differences in the length of time individual units are tracked (because games have different durations) and utilizes data that is normally censored (units that have not died, either because the game ended before they died or because the unit transformed before it died).
Terran units had the broadest range of survival rates: while only 4% of Reapers survived until the end of the game, a very respectable 45% of medivacs did. Nonetheless, most units were much more likely to die than survive.
Of Terran units that died during the game, Liberators were the most likely to die in the first minute of existence (33%) while Medivacs were the least likely (only 10%). Battlecruisers had the longest life expectancy of any Terran unit at 3.9 minutes. One BC managed to survive 27 minutes!
The life expectancies of bread-and-butter Terran infantry units (Marines and Marauders) are very similar and only about a minute and a half.
Protoss units had much higher overall survival rates than those of the other two races, generally greater than 25%.Perhaps unsurprisingly, Observers also had the single highest survival rate of any unit at 51%.
Two-thirds of High Templar and a third of Dark Templar were fated to become Archons. While only a quarter of Archons survived until the end of the game, this was a better chance than either kind of Templar had untransformed, especially Dark Templar.
Over half (59%) of Phoenixes and Zealots did not live even a minute! Dark Templar were not far behind in early mortality and follow a similar survival curve to Zealots.
On the other hand, Carriers had a life expectancy of 4.5 minutes, tied with Swarm Hosts for the longest mean survival rate of any unit in the game. Protoss units overall have longer survival times compared to Zerg and Terran units with 15 of 18 having >2 minutes survival time compared to just 6 of 13 for Zerg and 5 of 13 for Terran.
Zerg units had very low survivability overall. Only 2% of Banelings and 3% of zerglings survived until the end of the game! Even less than a fifth of Lurkers made it.
A similar proportion - about 15% - of Zerglings, Roaches, and Hydralisks ended up transformed into more powerful units. Nearly a third of Corruptors ended up as Brood Lords.
Two-thirds of Banelings did not survive past a minute. In fact, the life expectancy of a Baneling was 0.4 minutes, the shortest of any unit in the game! This is perhaps unsurprising considering their tendency to get morphed on the front lines. Zerglings were not much better at 0.6 minutes.
The longest-lived zergling that still perished before the game ended, managed to stay alive for over 20 minutes.
Most StarCraft 2 units did not survive until the end of their games; squishy front-line Tier 1 units were even unlikely to survive past their first minute. Unit life expectancies ranged from 0.4 to 4.5 minutes, with the longest expectancies for units with long-ranged, independent projectiles (Carriers and Swarm Hosts).
To browse through all of the visualizations at once, click here.
Thanks to ZephyrBlue for extracting the data from replays and providing their parser. Thanks to Keiras for suggesting the Kaplan-Meier methodology.