Outer crowds are much more effective than inner crowds. An inner crowd of size infinity performs about as well as an outer crowd of size two.
You can approximately halve outer crowd error (in this task) by going from one to two people (this wasn’t true in my Moscow task!). About 90% of outer crowd error can be removed by going from one to ten people; going from ten to infinity people only removes an additional 10%.
the longer someone waits between making two guesses, the less correlated their guesses are, and the more inner-crowd-wisdom-effect they gain from averaging those guesses.