I'd say 2 is a good number. They have seen the potential consequences a lot better (if this assumption proves to be false, then 1 is a good number, you can test

I'd say 2 is a good number. They have seen the potential consequences a lot better (if this assumption proves to be false, then 1 is a good number, you can test it by amount of people that feel greatly more knowledgeable about this topic), therefore, they have better knowledge to vote.