Yes, I agree that older polls should matter less. I actually take them out of my average altogether. My approach is use the data the pollsters give you in the cross-tabs, shape that data with the right voter sample assumptions, then you’ve got something. The problem is dishonest pollsters like NYT/Sienna coming out with that nonsense PA poll today, and the Arizona one for that matter. They actually have Harris trailing by only five with men in PA, and by on three with white ID in PA. Give me a break! Can’t do much with polls like that. All you can do is adjust using party ID in a case like that because the bad party ID impacts all other categories. I like your model. do you put it on a website or just forums like this?
My model is a simple (for me) Excel spreadsheet. I developed a formula in 2010 that converts a poll and margin of error into a probability of the leader actually winning. Nate Silver figured out the same formula in 2012 and built his fivethirtyeight website around it.
I collect up to 15 distinct polls per state, convert each to a probability, date-weight the probabilities into an overall state average, and then run a Monte Carlo simulation of 5,000 iterations to generate an outcome probability distribution.
New polls replace older polls by the same pollster. At this point in the election, I no longer use Registered Voter polls. I used to put out a weekly report here on Free Republic showing the changes in polls for the week, but I stopped putting that much effort into it due to the impacts of systemic voter fraud and push-poll bias. Now I just post snippets like today when an appropriate thread pops up.
I also do a Senate poll. As of now, Republicans have an 82.1% probability of winning the Senate, with an expected value of 51.79 seats.
Regarding adjusting for bias, I leave that to the "experts." I figure that extreme polling error will get washed out in the averages, especially if an outlier poll becomes stale against newer polls. I chose to make my report be on the polls as they are, since that tells a story, too. Hopefully, it ends up being the right one.
-PJ