We will judge casualties for the Ukraine war based on the sum of the UN estimate of civilian deaths + injuries, plus each side's report of the other side's deaths + injuries. See eg https://en.wikipedia.org/wiki/2022_Russian_invasion_of_Ukraine#Field_casualties_and_injuries . We reserve the right to change this if one side starts giving implausible numbers. When a range is offered, the midpoint of the range will be taken. If there is no easy way to determine which Ukraine casualties happened in 2022 vs. 2023, the current total of 225,216 will be subtracted from the best available end-of-2023 number. The casualty numbers for other wars will be calculated in a method as similar to this as possible; if an identical methodology cannot be used, we reserve the right to use credible third-party (eg US government, well-known neutral media outlet) estimates.
This is question #13 in the Astral Codex Ten 2023 Prediction Contest. The contest rules and full list of questions are available here. Market will resolve according to Scott Alexander’s judgment, as given through future posts on Astral Codex Ten.
If the Tigray war ceasefire does not hold, then seems like that war would be close: https://en.wikipedia.org/wiki/Casualties_of_the_Tigray_War#:~:text=According%20to%20researchers%20at%20Ghent,the%20world's%20bloodiest%20contemporary%20conflicts.%22