Economics growth and resource shortages. Many times it's seemed like we're imminently going to run out of some resource (coal in the 1890s, food scares in the 60s, global cooling, peak oil) and economic growth would grind to a halt. The details supported the view (existing coal seams were running low, etc.) but a reference class of other 20 year periods after 1800 would have suggested, correctly, that the economy would continue to grow at about 2-3%.

Alternatively, politics. Periodically it seems like one party has achieved a permanent stranglehold on power- the republican revolution, Obama a year ago, the conservatives in 1983, Labour in 1945, 1997 – but ignoring the details of the situation, and just looking at other decades, we’d’ve guessed correctly that the other party would rise again.

Recessions. While going into a recession, it always appears to be the Worst Thing Ever, and to signal the End of Capitalism; worse than 1929 for sure. Ignoring the details and looking at other recessions, we get a better, more moderate prediction.