It should be obvious that the current most powerful country and the biggest villain of the 20th century are outliers.
Chatgpt tells me the median country founded in the 18th century lasted 200 years. But I’m not sure about definitions. It also points out that you could plausibly consider the US Civil War as the country undergoing a regime change. It also expressed skepticism that the founders actually believed it would only last 50 years.
You’re filtering based on data that isn’t available at the time of the prediction. Number of traders at resolution isn’t known, and resolution time isn’t known for all markets at market creation. So calibration will have a lookahead bias.
You should ideally filter only based on info available at the time of the predictions you’re grading.