Almost all the ballots have been counted in the New York City municipal elections held yesterday. My last post here was on Sunday, but there was a late poll from Public Policy Polling that changed my numbers. After working on how I was going to consider the "median result" from a set of four polls in a three person race where there was a 40% threshold, my last prediction on Monday evening was posted to Twitter.
Final call on NYC Dem Mayor's race, different from
55% De Blasio 1st ballot
30% De Blasio/Thompson
15% De Blasio/Quinn
Professor Wang's last prediction was a 90% probability of De Blasio on the first ballot.
The current vote count has Bill De Blasio at 40.3% and his closest rival Bill Thompson at 26.2%. Because his margin over the 40% threshold is so slim, we will have to wait for absentee ballots and an automatic recount for a result this close. The reported estimate is next Monday for a conclusive result.
Here on the blog, I made no mention of the comptroller's race, but I did mention it on Twitter in a two part tweet.
NYC mayoral primary today.
If Spitzer loses the Comptroller race, full credit should go @QuinnipiacPoll, the only organization to favor his rival Stringer. [2/2]
There were several polls of this race as you can see at this link to the Real Clear Politics polling page. There was nothing that made this look like a close race until late August, with Eliot Spitzer's hopes for a political comeback looking very strong while Manhattan borough president Scott Stringer seemed unable to make any headway. But then Quinnipiac had a poll that said the race was tied, then another Quinnipiac poll had a small of 2% for Stringer on September 1, then a commanding 7% lead a week later.
The actual result was Stringer by 4%, 52% to 48%.
The reason my system - and Professor Wang's - favored Spitzer was that no other pollster agreed with Quinnipiac, not even once. After the first Quinnipiac poll that showed a close race, Siena, Marist and PPP all released polls, all of them favoring Spitzer.
So my system failed to predict this race. Often, when I get a race wrong, I try to find ways to adjust things to improve, but if I was given a similar situation tomorrow, I wouldn't change a thing. Here are my reasons.
1. I never weigh in more than a single poll from any polling company and always the most recent.
2. Because Quinnipiac only gets one result counted, they had one poll out of three in the final mix, along with PPP and Siena.
3. In a three poll situation, I take the median result, not the average of the three. Quinnipiac was the outlier, but outliers aren't often the closest to correct. Obviously, it will happen sometimes, but it is rare enough that I do not want to second guess myself in a situation like this. Polls miss the mark, sometimes by making bad assumptions, sometimes just by the fact that randomness is involved. For example, of the three polls Quinnipiac had the largest sample size, but that does not always (or even often) mean the most accurate. Looking at the mayoral polling and factoring out the undecided, Quinnipiac had De Blasio at 46% of the people who had a preference, while PPP had him at 42% and Siena had him at 39%. In this case, it's the low outlier that was closest.
So this means at least one more report on the mayor's race. It is widely agreed that the Republican primary winner Joe Llota will be very hard pressed to win in the general election. De Blasio got 260,000 votes in the Democratic primary, Llota finished first with over 50% in the Republican primary with about 30,000, which would have given him sixth place in the Democratic race.
And while I did not use their poll, I want to congratulate Quinnipiac for being alone with the correct result in the comptroller's race. It is a field filled with randomness, but they had Stringer with a chance or the lead three separate times in barely two weeks when no one else did. That's a record they can point to with pride.
No comments:
Post a Comment