I suspect many people responding to surveys about events which happened 10-30 years ago would be doing so with the aim of influencing the betting markets which affect near future policy.
It would be good to focus on questions for which that’s not so bad, because our goal is to measure some kind of general sentiment in the future—if in the future people feel like “we should now do more/less of X” then that’s pretty correlated with feeling like we did too little in the past (obviously not perfectly—we may have done too little 30 years ago but overcorrected 10 years ago—but if you are betting about public opinion in the US I don’t think you should ever be thinking about that kind of distinction).
E.g. I think this would be OK for:
Did we do too much or too little about climate change?
Did we have too much or too little immigration of various kinds?
Were we too favorable or too unfavorable to unions?
Were taxes too high or too low?
Is compensating organ at market rates a good idea?
And so forth.
I’m also very excited about this idea. The format of the ultimate judgement (i.e. the retrospective evaluation) seems important. A straightforward survey of the population suffers from the problem that teasing out an answer about the quality of a policy is hard, and most people won’t have put the time or effort in (even assuming they don’t have a hidden agenda, as John_Maxwell_IV highlights). But a survey of experts has its own problems too.
That said, I suspect these issues are surmountable, and would be keen to see this idea turn into action.