64 = Predictit marketbased probability that the Democrats
win the presidential election.
"sumvotes" is the sum of the electoral
votes of all the states ranked above the state
plus the state's vote. 270 votes are needed to win.
You can see that Michigan is the pivot state.
If Biden takes Michigan and all the
states ranked above it, he gets 279 votes. Of the states ranked below
Michigan, he
could also win by not taking Michigan, but taking Arizona,
where he is favored.
This would, of course, violate the ranking assumption.
According to the ranking assumption, the probability that the Democrats
get a majority in the electoral college is the
probability that they win the pivot state, Michigan,
which is 67.
On the Predictit website, the marketbased probability that
the Democrats win the
presidential election (in the electoral college) is 64, close to
67. So the market participants are roughly using the ranking
assumption.
Ranking Assumption for 2020 Senate elections

Data collected from Predictit on September 8, 2020
The current make up of the Senate is 53 Republicans and 47 Democrats, counting
the 2 independents as Democrats.
Only 14 states are in play in having market probabilities on the Predictit
website less than 90 percent
and greater than 10 percent. The 14 states ranked by the market probabilities
from Predictit for the Democratic candidate are:

state
 prob
 now

Colorado  88  R 
Arizona  87  R 
Minnesota  84  D 
Michigan  77  D 
Maine  72  R  pivot for 50 Democratic seats 
North Carolina  67  R  pivot for 51 Democratic seats 
Iowa  45  R 
Montana  41  R 
Georgia, reg.  30  R 
Alaska  26  R 
South Carolina  23  R 
Georgia, spec.  20  R 
Texas  13  R 
Alabama  11  R 
56 = Predictit marketbased probability of the Democrats controlling the
Senate.
If the Democrats win North Carolina and all the states above it, they will have
51 seats, counting the 2 independents as Democrats. If they win
Maine and all the states above it but lose North Carolina, they will have 50
seats. They will still control the Senate if they win the White House.
According to the ranking assumption, the Predictit market
probablility that they control the Senate is thus 72 percent (the
probablity they win Maine) if they win the White House and 67 percent
(the probablility they win North Carolina) if they don't.
If we use the Predictit marketbased probabilty of 60 percent that the
Democrats win
the presidential electon, then the ranking assumption
probability that the Democrats
control the Senate is 0.60x72 + 0.40x67, which is 70 percent.
This is noticeably higher than the Predictit marketbased probability
of the Democrats controlling the Senate of 56 percent. In this case, unlike
in the Presidential case, it does not look like the market is using the
ranking assumption.
Data collected from Predictit on September 22, 2020
The current make up of the Senate is 53 Republicans and 47 Democrats, counting
the 2 independents as Democrats.
Only 16 states are in play in having market probabilities on the Predictit
website less than 90 percent
and greater than 10 percent. The 16 states ranked by the market probabilities
from Predictit for the Democratic candidate are:

state
 prob
 now

Minnesota  87  D 
Colorado  84  R 
Arizona  83  R 
Michigan  73  D 
Maine  73  R  pivot for 50 Democratic seats 
North Carolina  65  R  pivot for 51 Democratic seats 
Iowa  49  R 
Montana  42  R 
Georgia, reg.  35  R 
South Carolina  30  R 
Georgia, spec.  27  R 
Alaska  26  R 
Kansas  22  R 
Texas  16  R 
Alabama  12  R 
Kentucky  11  R 
57 = Predictit marketbased probability of the Democrats controlling the
Senate.
If the Democrats win North Carolina and all the states above it, they will have
51 seats, counting the 2 independents as Democrats. If they win
Maine and all the states above it but lose North Carolina, they will have 50
seats. They will still control the Senate if they win the White House.
According to the ranking assumption, the Predictit market
probablility that they control the Senate is thus 73 percent (the
probablity they win Maine) if they win the White House and 65 percent
(the probablility they win North Carolina) if they don't.
If we use the Predictit marketbased probabilty of 59 percent that the
Democrats win
the presidential electon, then the ranking assumption
probability that the Democrats
control the Senate is 0.59x73 + 0.41x65, which is 70 percent.
This is noticeably higher than the Predictit marketbased probability
of the Democrats controlling the Senate of 57 percent. In this case, unlike
in the Presidential case, it does not look like the market is using the
ranking assumption.
Data collected from Predictit on October 6, 2020
The current make up of the Senate is 53 Republicans and 47 Democrats, counting
the 2 independents as Democrats.
Only 16 states are in play in having market probabilities on the Predictit
website less than 90 percent
and greater than 10 percent. The 16 states ranked by the market probabilities
from Predictit for the Democratic candidate are:

state
 prob
 now

Colorado  87  R 
Arizona  83  R 
Maine  77  R  pivot for 50 Democratic seats 
Michigan  71  D 
North Carolina  58  R  pivot for 51 Democratic seats 
Iowa  54  R 
Montana  42  R 
Georgia, reg.  38  R 
Georgia, spec.  34  R 
Alaska  34  R 
South Carolina  32  R 
Kansas  31  R 
Mississippi  19  R 
Texas  18  R 
Alabama  13  R 
Kentucky  11  R 
66 = Predictit marketbased probability of the Democrats controlling the
Senate.
If the Democrats win North Carolina and all the states above it, they will have
51 seats, counting the 2 independents as Democrats. If they win
Maine and all the states above it but lose North Carolina, they will have 50
seats. They will still control the Senate if they win the White House.
According to the ranking assumption, the Predictit market
probablility that they control the Senate is thus 77 percent (the
probablity they win Maine) if they win the White House and 58 percent
(the probablility they win North Carolina) if they don't.
If we use the Predictit marketbased probabilty of 66 percent that the
Democrats win
the presidential electon, then the ranking assumption
probability that the Democrats
control the Senate is 0.66x77 + 0.34x58, which is 70.5 percent.
This is somewhat higher
than the Predictit marketbased probability
of the Democrats controlling the Senate of 66 percent. So the market is not
quite using the ranking asssumption.
Data collected from Predictit on October 20, 2020
The current make up of the Senate is 53 Republicans and 47 Democrats, counting
the 2 independents as Democrats.
Only 16 states are in play in having market probabilities on the Predictit
website less than 90 percent
and greater than 10 percent. The 16 states ranked by the market probabilities
from Predictit for the Democratic candidate are:

state
 prob
 now

Minnesota  87  D 
Colorado  87  R 
Arizona  80  R 
Maine  76  R 
Michigan  64  D 
North Carolina  60  R  pivot for 50 Democratic seats 
Iowa  60  R  pivot for 51 Democratic seats 
Georgia, spec.  43  R 
Montana  37  R 
Georgia, reg.  37  R 
South Carolina  27  R 
Kansas  26  R 
Alaska  24  R 
Texas  23  R 
Mississippi  14  R 
Alabama  13  D 
65 = Predictit marketbased probability of the Democrats controlling the
Senate.
If the Democrats win Iowa and all the states above it, they will have
51 seats, counting the 2 independents as Democrats, and assuming that they
lose Alabama. If they win
North Carolina and all the states above it but lose Iowa, they will have 50
seats. They will still control the Senate if they win the White House.
According to the ranking assumption, the Predictit market
probablility that they control the Senate is thus 60 percent (the
probablity they win North Carolina) if they win the White House and also
60 percent
(the probablility they win Iowa) if they don't.
If we use the Predictit marketbased probabilty of 65 percent that the
Democrats win
the presidential electon, then the ranking assumption
probability that the Democrats
control the Senate is 0.65x60 + 0.35x60, which is 60 percent.
This is slightly smaller
than the Predictit marketbased probability
of the Democrats controlling the Senate of 65 percent. So the market is not
quite using the ranking asssumption.
 