Sunday 30 December 2018

Farewell 2018 - Vic Review

Final, we have the Victorian election to review. 88 Legislative Assembly seats and 40 Legislative Council seats were up for election: the full Victorian parliament.

Legislative Assembly


74 seats, or 84.1%, were predicted correctly.


Seat Prediction Result
Albert Park  ALP ALP
Altona  ALP ALP
Bass  LIB ALP
Bayswater  LIB ALP
Bellarine  ALP ALP
Benambra  LIB LIB
Bendigo East  ALP ALP
Bendigo West  ALP ALP
Bentleigh  ALP ALP
Box Hill  LIB ALP
Brighton  LIB LIB
Broadmeadows  ALP ALP
Brunswick ALP GRN
Bulleen  LIB LIB
Bundoora  ALP ALP
Buninyong  ALP ALP
Burwood  ALP ALP
Carrum  ALP ALP
Caulfield  LIB LIB
Clarinda  ALP ALP
Cranbourne  ALP ALP
Croydon  LIB LIB
Dandenong  ALP ALP
Eildon  ALP LIB
Eltham  ALP ALP
Essendon  ALP ALP
Euroa  NAT NAT
Evelyn  LIB LIB
Ferntree Gully  LIB LIB
Footscray  ALP ALP
Forest Hill  LIB LIB
Frankston  ALP ALP
Geelong  ALP ALP
Gembrook  LIB LIB
Gippsland East  NAT NAT
Gippsland South  NAT NAT
Hastings  LIB LIB
Hawthorn  LIB ALP
Ivanhoe  ALP ALP
Kew  LIB LIB
Keysborough  ALP ALP
Kororoit  ALP ALP
Lara  ALP ALP
Lowan  NAT NAT
Macedon  ALP ALP
Malvern  LIB LIB
Melbourne ALP GRN
Melton  ALP ALP
Mildura NAT IND
Mill Park  ALP ALP
Monbulk  ALP ALP
Mordialloc  ALP ALP
Mornington  LIB LIB
Morwell  ALP IND
Mount Waverley  LIB ALP
Mulgrave  ALP ALP
Murray Plains  NAT NAT
Narracan  LIB LIB
Narre Warren North  ALP ALP
Narre Warren South  ALP ALP
Nepean  LIB ALP
Niddrie  ALP ALP
Northcote GRN ALP
Oakleigh  ALP ALP
Ovens Valley  NAT NAT
Pascoe Vale  ALP ALP
Polwarth  LIB LIB
Prahran GRN GRN
Preston  ALP ALP
Richmond ALP ALP
Ringwood  LIB ALP
Ripon  ALP LIB
Rowville  LIB LIB
Sandringham  LIB LIB
Shepparton IND IND
South Barwon  ALP ALP
South-West Coast  LIB LIB
St Albans  ALP ALP
Sunbury  ALP ALP
Sydenham  ALP ALP
Tarneit  ALP ALP
Thomastown  ALP ALP
Warrandyte  LIB LIB
Wendouree  ALP ALP
Werribee  ALP ALP
Williamstown  ALP ALP
Yan Yean  ALP ALP
Yuroke  ALP ALP

The 14 incorrect predictions were:


Seat Prediction Result
Bass  LIB ALP
Bayswater  LIB ALP
Box Hill  LIB ALP
Brunswick ALP GRN
Eildon  ALP LIB
Hawthorn  LIB ALP
Melbourne ALP GRN
Mildura NAT IND
Morwell  ALP IND
Mount Waverley  LIB ALP
Nepean  LIB ALP
Northcote GRN ALP
Ringwood  LIB ALP
Ripon  ALP LIB

Mildura and Morwell saw independents elected. Because it is not feasible to look into the prospects of every independent running in every seat, I accepted long ago that upsets of this nature are unpredictable in practical terms.

I had also noted at the foot of my predictions that, for unempirical reasons, I expected the greens to pick up a few seats not officially predicted, and singled out Melbourne as likely to be retained. I do not consider Melbourne or Brunswick to be surprises.

Eildon and Ripon were retained by Liberal incumbents against the swing and remain very narrow as a result. ABC has Ripon held by the Liberal party with 50.0% of the final count, meaning there were only a handful of ballots between the major parties in the end. Eildon is a little less precarious, but with 52.4% of the vote we came very close to being right in both cases, and I think these are acceptable mistakes.

Northcote was held by the Greens, but only as the result of a by-election, the Liberals did not contest. I do not think the lack of Liberal contest in that by-election makes that data unreliable, as traditional liberal voters would have allocated their votes exactly as their preferences in a contested election. However, the by-election may have been atypical for the focus it provided on local issues. The Greens certainly still poll well here, but despite the ABC indicating a swing in their favour (compared to the general election, not the by-election) they did finish second. I am in two minds as to whether this is a reason to be more cautious with by-election data and incumbents or just part of the usual statistical hurley-burley.

The remaining seven seats (Bass, Bayswater, Box Hill, Hawthorn, Mount Waverley, Nepean and Ringwood) are evidence that I underestimated the swing to the ALP in this election. It is true that this swing was far higher than most predicted, but being wrong en mass is little consolation. Previous work on predicting the size and distribution of swings is required, though past efforts have provided little encouragement. Nevertheless, these are seven seats out of 88, and a mid-80% accuracy overall is both typical and acceptable.

Legislative Council


The LegCo results were more chaotic by far.



As with all proportional, preferential votes, the final member from each division is always unpredictable, so the districts with scores of 4/5 are perfectly acceptable to me despite the patchwork of colours in the infographic above.

The total prediction score of 30/40 or 75% would be disappointing in a race of single-member seats like the Legislative Assembly, but this inherently difficult fifth-member prediction means a score above 80% would be outstanding. The remaining 20% are inevitably written off in almost every case as tossups for the same reason seats won by independents are not considered particularly concerning in the lower houses.

The areas of concern, then, are the Southern Metropolitan district and both the Northern and Western regional districts.

In South Metro, the ALP gained from the Greens, and the Reason Party (formerly the Australian Sex Party) took the scraps from both sides to earn the 5th seat. This is the first time a party outside of the major trio (ALP, LIB and GRN) have won a seat in South Metro and though they did get a mention in the prediction, this is unexpected based on the earlier polling. Similarly, for the Greens to consistently poll 90% of a quota historically would seem to guarantee them a seat, but this year they were closer to 77%. Both errors here demonstrate that historical data makes for poor predictions of the future, though the absence of alternative numbers is an issue we will struggle to overcome.

In the regional districts, the Liberals lost ground to several minor parties too--a cause of errors in the 5th seat of other districts also (Metro East and Metro South East in particular). Again, this is the errors of past data being used predictively. It is evident the Liberals' support from previous years was not present in 2018. One predicted shooters seat in Vic West was also lost as part of the general uncertainty and minor-party chaos of the 5th post, but I'm more impressed that I called them correctly in Vic East (and got a full 5/5 in that district).

The lessons of the Legislative Council predictions then are that tossups should be used liberally if this blog still handed those out, and that past data is poor predictively but more or less all that was available.

Farewell 2018 - US review

The holiday season can no longer distract me from my responsibility to summarise the past two elections discussed on this blog. The first is the US Mid-Terms, where predictions were made for the House, the Senate and the Gubernatorial races.

The House


The methodology applied in the House predictions can be found here, but in brief it awarded uncontested elections and the widely accepted safe-rated seats to their presumed winners, then seats with a 2% polling margin, then an aggregation of available data including polling, predicted swings and third-party assessments.

The results are as follows:


District Prediction Result
Alabama 1st Republican Republican
Alabama 2nd Republican Republican
Alabama 3rd Republican Republican
Alabama 4th Republican Republican
Alabama 5th Republican Republican
Alabama 6th Republican Republican
Alabama 7th Democrat Democrat
Alaska at large Republican Republican
Arizona 1st Democrat Democrat
Arizona 2nd Democrat Democrat
Arizona 3rd Democrat Democrat
Arizona 4th Republican Republican
Arizona 5th Republican Republican
Arizona 6th Republican Republican
Arizona 7th Democrat Democrat
Arizona 8th Republican Republican
Arizona 9th Democrat Democrat
Arkansas 1st Republican Republican
Arkansas 2nd Republican Republican
Arkansas 3rd Republican Republican
Arkansas 4th Republican Republican
California 1st Republican Republican
California 2nd Democrat Democrat
California 3rd Republican Democrat
California 4th Republican Republican
California 5th Democrat Democrat
California 6th Democrat Democrat
California 7th Democrat Democrat
California 8th Republican Republican
California 9th Democrat Democrat
California 10th Democrat Democrat
California 11th Democrat Democrat
California 12th Democrat Democrat
California 13th Democrat Democrat
California 14th Democrat Democrat
California 15th Democrat Democrat
California 16th Democrat Democrat
California 17th Democrat Democrat
California 18th Democrat Democrat
California 19th Democrat Democrat
California 20th Democrat Democrat
California 21st Republican Democrat
California 22nd Republican Republican
California 23rd Republican Republican
California 24th Democrat Democrat
California 25th Republican Democrat
California 26th Democrat Democrat
California 27th Democrat Democrat
California 28th Democrat Democrat
California 29th Democrat Democrat
California 30th Democrat Democrat
California 31st Democrat Democrat
California 32nd Democrat Democrat
California 33rd Democrat Democrat
California 34th Democrat Democrat
California 35th Democrat Democrat
California 36th Democrat Democrat
California 37th Democrat Democrat
California 38th Democrat Democrat
California 39th Democrat Democrat
California 40th Democrat Democrat
California 41st Democrat Democrat
California 42nd Republican Republican
California 43rd Democrat Democrat
California 44th Democrat Democrat
California 45th Republican Democrat
California 46th Democrat Democrat
California 47th Democrat Democrat
California 48th Republican Democrat
California 49th Democrat Democrat
California 50th Republican Republican
California 51st Democrat Democrat
California 52nd Democrat Democrat
California 53rd Democrat Democrat
Colorado 1st Democrat Democrat
Colorado 2nd Democrat Democrat
Colorado 3rd Republican Republican
Colorado 4th Republican Republican
Colorado 5th Republican Republican
Colorado 6th Democrat Democrat
Colorado 7th Democrat Democrat
Connecticut 1st Democrat Democrat
Connecticut 2nd Democrat Democrat
Connecticut 3rd Democrat Democrat
Connecticut 4th Democrat Democrat
Connecticut 5th Democrat Democrat
Delaware at large  Democrat Democrat
Florida 1st Republican Republican
Florida 2nd Republican Republican
Florida 3rd Republican Republican
Florida 4th Republican Republican
Florida 5th Democrat Democrat
Florida 6th Republican Republican
Florida 7th Democrat Democrat
Florida 8th Republican Republican
Florida 9th Democrat Democrat
Florida 10th Democrat Democrat
Florida 11th Republican Republican
Florida 12th Republican Republican
Florida 13th Democrat Democrat
Florida 14th Democrat Democrat
Florida 15th Republican Republican
Florida 16th Republican Republican
Florida 17th Republican Republican
Florida 18th Republican Republican
Florida 19th Republican Republican
Florida 20th Democrat Democrat
Florida 21st Democrat Democrat
Florida 22nd Democrat Democrat
Florida 23rd Democrat Democrat
Florida 24th Democrat Democrat
Florida 25th Republican Republican
Florida 26th Democrat Democrat
Florida 27th Democrat Democrat
Georgia 1st Republican Republican
Georgia 2nd Democrat Democrat
Georgia 3rd Republican Republican
Georgia 4th Democrat Democrat
Georgia 5th Democrat Democrat
Georgia 6th Republican Democrat
Georgia 7th Republican Republican
Georgia 8th Republican Republican
Georgia 9th Republican Republican
Georgia 10th Republican Republican
Georgia 11th Republican Republican
Georgia 12th Republican Republican
Georgia 13th Democrat Democrat
Georgia 14th Republican Republican
Hawaii 1st Democrat Democrat
Hawaii 2nd Democrat Democrat
Idaho 1st Republican Republican
Idaho 2nd Republican Republican
Illinois 1st Democrat Democrat
Illinois 2nd Democrat Democrat
Illinois 3rd Democrat Democrat
Illinois 4th Democrat Democrat
Illinois 5th Democrat Democrat
Illinois 6th Democrat Democrat
Illinois 7th Democrat Democrat
Illinois 8th Democrat Democrat
Illinois 9th Democrat Democrat
Illinois 10th Democrat Democrat
Illinois 11th Democrat Democrat
Illinois 12th Republican Republican
Illinois 13th Republican Republican
Illinois 14th Republican Democrat
Illinois 15th Republican Republican
Illinois 16th Republican Republican
Illinois 17th Democrat Democrat
Illinois 18th Republican Republican
Indiana 1st Democrat Democrat
Indiana 2nd Republican Republican
Indiana 3rd Republican Republican
Indiana 4th Republican Republican
Indiana 5th Republican Republican
Indiana 6th Republican Republican
Indiana 7th Democrat Democrat
Indiana 8th Republican Republican
Indiana 9th Republican Republican
Iowa 1st Democrat Democrat
Iowa 2nd Democrat Democrat
Iowa 3rd Democrat Democrat
Iowa 4th Republican Republican
Kansas 1st Republican Republican
Kansas 2nd Democrat Republican
Kansas 3rd Democrat Democrat
Kansas 4th Republican Republican
Kentucky 1st Republican Republican
Kentucky 2nd Republican Republican
Kentucky 3rd Democrat Democrat
Kentucky 4th Republican Republican
Kentucky 5th Republican Republican
Kentucky 6th Republican Republican
Louisiana 1st Republican Republican
Louisiana 2nd Democrat Democrat
Louisiana 3rd Republican Republican
Louisiana 4th Republican Republican
Louisiana 5th Republican Republican
Louisiana 6th Republican Republican
Maine 1st Democrat Democrat
Maine 2nd Democrat Democrat
Maryland 1st Republican Republican
Maryland 2nd Democrat Democrat
Maryland 3rd Democrat Democrat
Maryland 4th Democrat Democrat
Maryland 5th Democrat Democrat
Maryland 6th Democrat Democrat
Maryland 7th Democrat Democrat
Maryland 8th Democrat Democrat
Massachusetts 1st Democrat Democrat
Massachusetts 2nd Democrat Democrat
Massachusetts 3rd Democrat Democrat
Massachusetts 4th Democrat Democrat
Massachusetts 5th Democrat Democrat
Massachusetts 6th Democrat Democrat
Massachusetts 7th Democrat Democrat
Massachusetts 8th Democrat Democrat
Massachusetts 9th Democrat Democrat
Michigan 1st Republican Republican
Michigan 2nd Republican Republican
Michigan 3rd Republican Republican
Michigan 4th Republican Republican
Michigan 5th Democrat Democrat
Michigan 6th Republican Republican
Michigan 7th Republican Republican
Michigan 8th Republican Democrat
Michigan 9th Democrat Democrat
Michigan 10th Republican Republican
Michigan 11th Democrat Democrat
Michigan 12th Democrat Democrat
Michigan 13th Democrat Democrat
Michigan 14th Democrat Democrat
Minnesota 1st Democrat Republican
Minnesota 2nd Democrat Democrat
Minnesota 3rd Democrat Democrat
Minnesota 4th Democrat Democrat
Minnesota 5th Democrat Democrat
Minnesota 6th Republican Republican
Minnesota 7th Democrat Democrat
Minnesota 8th Republican Republican
Mississippi 1st Republican Republican
Mississippi 2nd Democrat Democrat
Mississippi 3rd Republican Republican
Mississippi 4th Republican Republican
Missouri 1st Democrat Democrat
Missouri 2nd Republican Republican
Missouri 3rd Republican Republican
Missouri 4th Republican Republican
Missouri 5th Democrat Democrat
Missouri 6th Republican Republican
Missouri 7th Republican Republican
Missouri 8th Republican Republican
Montana at large Republican Republican
Nebraska 1st Republican Republican
Nebraska 2nd Republican Republican
Nebraska 3rd Republican Republican
Nevada 1st Democrat Democrat
Nevada 2nd Republican Republican
Nevada 3rd Democrat Democrat
Nevada 4th Democrat Democrat
New Hampshire 1st Democrat Democrat
New Hampshire 2nd Democrat Democrat
New Jersey 1st Democrat Democrat
New Jersey 2nd Democrat Democrat
New Jersey 3rd Republican Democrat
New Jersey 4th Republican Republican
New Jersey 5th Democrat Democrat
New Jersey 6th Democrat Democrat
New Jersey 7th Democrat Democrat
New Jersey 8th Democrat Democrat
New Jersey 9th Democrat Democrat
New Jersey 10th Democrat Democrat
New Jersey 11th Democrat Democrat
New Jersey 12th Democrat Democrat
New Mexico 1st Democrat Democrat
New Mexico 2nd Republican Democrat
New Mexico 3rd Democrat Democrat
New York 1st Republican Republican
New York 2nd Republican Republican
New York 3rd Democrat Democrat
New York 4th Democrat Democrat
New York 5th Democrat Democrat
New York 6th Democrat Democrat
New York 7th Democrat Democrat
New York 8th Democrat Democrat
New York 9th Democrat Democrat
New York 10th Democrat Democrat
New York 11th Republican Democrat
New York 12th Democrat Democrat
New York 13th Democrat Democrat
New York 14th Democrat Democrat
New York 15th Democrat Democrat
New York 16th Democrat Democrat
New York 17th Democrat Democrat
New York 18th Democrat Democrat
New York 19th Democrat Democrat
New York 20th Democrat Democrat
New York 21st Republican Republican
New York 22nd Democrat Democrat
New York 23rd Republican Republican
New York 24th Republican Republican
New York 25th Democrat Democrat
New York 26th Democrat Democrat
New York 27th Republican Republican
North Carolina 1st Democrat Democrat
North Carolina 2nd Republican Republican
North Carolina 3rd Republican Republican
North Carolina 4th Democrat Democrat
North Carolina 5th Republican Republican
North Carolina 6th Republican Republican
North Carolina 7th Republican Republican
North Carolina 8th Republican Republican
North Carolina 9th Republican Republican
North Carolina 10th Republican Republican
North Carolina 11th Republican Republican
North Carolina 12th Democrat Democrat
North Carolina 13th Republican Republican
North Dakota at large Republican Republican
Ohio 1st Republican Republican
Ohio 2nd Republican Republican
Ohio 3rd Democrat Democrat
Ohio 4th Republican Republican
Ohio 5th Republican Republican
Ohio 6th Republican Republican
Ohio 7th Republican Republican
Ohio 8th Republican Republican
Ohio 9th Democrat Democrat
Ohio 10th Republican Republican
Ohio 11th Democrat Democrat
Ohio 12th Republican Republican
Ohio 13th Democrat Democrat
Ohio 14th Republican Republican
Ohio 15th Republican Republican
Ohio 16th Republican Republican
Oklahoma 1st Republican Republican
Oklahoma 2nd Republican Republican
Oklahoma 3rd Republican Republican
Oklahoma 4th Republican Republican
Oklahoma 5th Republican Democrat
Oregon 1st Democrat Democrat
Oregon 2nd Republican Republican
Oregon 3rd Democrat Democrat
Oregon 4th Democrat Democrat
Oregon 5th Democrat Democrat
Pennsylvania 1st Republican Republican
Pennsylvania 2nd Democrat Democrat
Pennsylvania 3rd Republican Democrat
Pennsylvania 4th Republican Democrat
Pennsylvania 5th Democrat Democrat
Pennsylvania 6th Democrat Democrat
Pennsylvania 7th Democrat Democrat
Pennsylvania 8th Democrat Democrat
Pennsylvania 9th Republican Republican
Pennsylvania 10th Republican Republican
Pennsylvania 11th Republican Republican
Pennsylvania 12th Republican Republican
Pennsylvania 13th Democrat Republican
Pennsylvania 14th Republican Republican
Pennsylvania 15th Republican Republican
Pennsylvania 16th Democrat Republican
Pennsylvania 17th Democrat Democrat
Pennsylvania 18th Democrat Democrat
Rhode Island 1st Democrat Democrat
Rhode Island 2nd Democrat Democrat
South Carolina 1st Republican Democrat
South Carolina 2nd Republican Republican
South Carolina 3rd Republican Republican
South Carolina 4th Republican Republican
South Carolina 5th Republican Republican
South Carolina 6th Democrat Democrat
South Carolina 7th Republican Republican
South Dakota at large Republican Republican
Tennessee 1st Republican Republican
Tennessee 2nd Republican Republican
Tennessee 3rd Republican Republican
Tennessee 4th Republican Republican
Tennessee 5th Democrat Democrat
Tennessee 6th Republican Republican
Tennessee 7th Republican Republican
Tennessee 8th Republican Republican
Tennessee 9th Democrat Democrat
Texas 1st Republican Republican
Texas 2nd Republican Republican
Texas 3rd Republican Republican
Texas 4th Republican Republican
Texas 5th Republican Republican
Texas 6th Republican Republican
Texas 7th Republican Democrat
Texas 8th Republican Republican
Texas 9th Democrat Democrat
Texas 10th Republican Republican
Texas 11th Republican Republican
Texas 12th Republican Republican
Texas 13th Republican Republican
Texas 14th Republican Republican
Texas 15th Democrat Democrat
Texas 16th Democrat Democrat
Texas 17th Republican Republican
Texas 18th Democrat Democrat
Texas 19th Republican Republican
Texas 20th Democrat Democrat
Texas 21st Republican Republican
Texas 22nd Republican Republican
Texas 23rd Republican Republican
Texas 24th Republican Republican
Texas 25th Republican Republican
Texas 26th Republican Republican
Texas 27th Republican Republican
Texas 28th Democrat Democrat
Texas 29th Democrat Democrat
Texas 30th Democrat Democrat
Texas 31st  Republican Republican
Texas 32nd Republican Democrat
Texas 33rd Democrat Democrat
Texas 34th Democrat Democrat
Texas 35th Democrat Democrat
Texas 36th Republican Republican
Utah 1st Republican Republican
Utah 2nd Republican Republican
Utah 3rd Republican Republican
Utah 4th Democrat Democrat
Vermont at large Democrat Democrat
Virginia 1st Republican Republican
Virginia 2nd Republican Democrat
Virginia 3rd Democrat Democrat
Virginia 4th Democrat Democrat
Virginia 5th Republican Republican
Virginia 6th Republican Republican
Virginia 7th Democrat Democrat
Virginia 8th Democrat Democrat
Virginia 9th Republican Republican
Virginia 10th Democrat Democrat
Virginia 11th Democrat Democrat
Washington 1st Democrat Democrat
Washington 2nd Democrat Democrat
Washington 3rd Republican Republican
Washington 4th Republican Republican
Washington 5th Republican Republican
Washington 6th Democrat Democrat
Washington 7th Democrat Democrat
Washington 8th Republican Democrat
Washington 9th Democrat Democrat
Washington 10th Democrat Democrat
West Virginia 1st Republican Republican
West Virginia 2nd Republican Republican
West Virginia 3rd Republican Republican
Wisconsin 1st Republican Republican
Wisconsin 2nd Democrat Democrat
Wisconsin 3rd Democrat Democrat
Wisconsin 4th Democrat Democrat
Wisconsin 5th Republican Republican
Wisconsin 6th Republican Republican
Wisconsin 7th Republican Republican
Wisconsin 8th Republican Republican
Wyoming at large Republican Republican

That's not a bad result. Of the 435 predictions, 412 (or 94.7%) were correct.

The 23 that were wrong were:


District Prediction Result
California 3rd Republican Democrat
California 21st Republican Democrat
California 25th Republican Democrat
California 45th Republican Democrat
California 48th Republican Democrat
Georgia 6th Republican Democrat
Illinois 14th Republican Democrat
Kansas 2nd Democrat Republican
Michigan 8th Republican Democrat
Minnesota 1st Democrat Republican
New Jersey 3rd Republican Democrat
New Mexico 2nd Republican Democrat
New York 11th Republican Democrat
Oklahoma 5th Republican Democrat
Pennsylvania 3rd Republican Democrat
Pennsylvania 4th Republican Democrat
Pennsylvania 13th Democrat Republican
Pennsylvania 16th Democrat Republican
South Carolina 1st Republican Democrat
Texas 7th Republican Democrat
Texas 32nd Republican Democrat
Virginia 2nd Republican Democrat
Washington 8th Republican Democrat

Most of these are examples of seats where I backed the incumbent who then lost on a very narrow margin. At first, looking at the large number of blue results here, I assumed this was an indication of me being cautiously skeptical about the 'blue wave' narrative, but could also indicate that we gave just a little too much weight to the value of incumbency.


District Percentage Points in excess of 50
California 21st 0.4
California 25th 4.4 
California 45th 2.1
California 48th 3.6
Georgia 6th 0.5
Illinois 14th 2.5
Michigan 8th 0.6
Minnesota 1st 5.7
New Mexico 2nd 0.9
New York 11th 3.0
Oklahoma 5th 0.7
South Carolina 1st 0.7
Texas 7th 2.5
Texas 32nd 2.3
Virginia 2nd 1.1
Washington 8th 2.4

California and Minnesota, among these districts, are the only states with concerning margins of error. There were other classes of mistake, though. In California 3 the incumbent was unexpectedly re-elected with an 8.1%, contrary to an average "Likely Republican" rating among third parties and no targeted polling. The previous special election in the district may be responsible for this. In Kansas 2 and New Jersey 3, the seats were won by parties I had not predicted, though neither polled over 50.0% and the impact of Libertarian and Independent votes may have skewed the results. And then there was Pensylvania.

Most of the above I am reasonably content with as the normal variation of an electoral system, with perhaps a little need to tweak the weighting I give to incumbency. Pensylvania, however, was a significant oversight. The 16th district saw the incumbent returned with 51.6% of the vote and I can accept that. However the 4th, 13th and particularly the 3rd district are another matter.

Pennsylvania 4 was won by the Dems with 63.5% of the vote. This is in contrast with 66.1% for the Republicans in 2016 and 74.5% in 2014. That is one hefty swing, and at least in the data I was looking for there was nothing to indicate it. In fact, there was no indicator of anything--no 3rd party rating, no district-specific polling. This is typical of safe seats, as Penn 4 turned out to be, but usually safe seats are not swing seats.

Simmilar story for Penn 13 but in reverse. No recent data, but it appeared safe for the Democrats based on past voting and was won decisively by the GOP with 70.5% of the vote. In fact, this district was so safe for the Democrats historically the Republicans didn't even contest it in 2016.

Pennsylvania's 3rd district is even more extreme. Increasingly safe for the Republicans since they took posession in 2010, the Dem's didn't even contest it last election. This election though? Democrat won with 93.4% of the vote. 93.4%.

So what happened in Pensylvania that I missed was a whole bunch of redistricting that shoved safe incumbents into other seats and completely wrote off all the historical data i was relying on. That was a pretty important fact I overlooked, though I'm not sure I would have been able to get accurate data for these districts anyhow.

On the whole, though, quite a pleasing result.

The Senate


Four errors in senate predictions occured this year.


State Prediction Result
Arizona Republican Democrat
California Democrat Democrat
Connecticut Democrat Democrat
Delaware Democrat Democrat
Florida Republican Republican
Hawaii Democrat Democrat
Indiana Democrat Republican
Maine Independent Independent
Maryland Democrat Democrat
Massachusetts Democrat Democrat
Michigan Democrat Democrat
Minnesota Democrat Democrat
Minnesota (s) Democrat Democrat
Mississippi Republican Republican
Mississippi (s) Republican Republican
Missouri Democrat Republican
Montana Democrat Democrat
Nebraska Republican Republican
Nevada Republican Democrat
New Jersey Democrat Democrat
New Mexico Democrat Democrat
New York Democrat Democrat
North Dakota Republican Republican
Ohio Democrat Democrat
Pennsylvania Democrat Democrat
Rhode Island Democrat Democrat
Tennessee Republican Republican
Texas Republican Republican
Utah Republican Republican
Vermont Independent Independent
Virginia Democrat Democrat
Washington Democrat Democrat
West Virginia Democrat Democrat
Wisconsin Democrat Democrat
Wyoming Republican Republican

Mildly interestingly, these errors cancelled out so my net prediction was spot on: 22 Dems, 11 Republicans and two Independents. On a case by case basis, the 4 errors out of 35 seats is a success rate of 88.6%. Nothing exceptional, but not terrible either.

All four of these errors were seats decided at the very end of the post, based on the subjective weighting of factors under the heading "final races". This is unsurprising--the hardest seats to determine are the most likely to be called wrongly. On the upside, it does endorse the methodology used earlier in my predictions, which had a 100% predictive success rate this year. On the downside, of the five seats I called by personal judgement, I got four wrong. Florida alone came through. So that's a little dispointing.

The Gubernators


In the 36 races for governor, five predictions were incorrect. This leaves a middling success rate of 86.1%.


State Prediction Results
Alabama Republican Republican
Alaska Republican Republican
Arizona Republican Republican
Arkansas Republican Republican
California Democrat Democrat
Colorado Democrat Democrat
Connecticut Democrat Democrat
Florida Democrat Republican
Georgia Republican Republican
Hawaii Democrat Democrat
Idaho Republican Republican
Illinois Democrat Democrat
Iowa Democrat Republican
Kansas Republican Democrat
Maine Democrat Democrat
Maryland Republican Republican
Massachusetts Republican Republican
Michigan Democrat Democrat
Minnesota Democrat Democrat
Nebraska Republican Republican
Nevada Republican Democrat
New Hampshire Republican Republican
New Mexico Democrat Democrat
New York Democrat Democrat
Ohio Democrat Republican
Oklahoma Republican Republican
Oregon Democrat Democrat
Pennsylvania Democrat Democrat
Rhode Island Democrat Democrat
South Carolina Republican Republican
South Dakota Republican Republican
Tennessee Republican Republican
Texas Republican Republican
Vermont Republican Republican
Wisconsin Democrat Democrat
Wyoming Republican Republican

Three races tipped for the Democrats (Florida, Iowa and Ohio) went to the GOP, and two Republican predictions (Kansas and Navada) went the other way. Sustained polling success for the Dems in Florida did not translate on the one vote that actually counted. The other four predictions were based on very limited data and noted as dubious in the relevant post. These were only called because I had to bet one way or the other, and I am not at all surprised I got them wrong.