Data collected from PredictWise on September 8, 2016

The current make up of the Senate is 54 Republicans and 46 Democrats, counting the 2 independents as Democrats. Only 12 states are in play in having market probabilities on the PredictWise website less than 90 percent and greater than 10 percent. The 12 states ranked by the market probabilities from PredictWise for the Democratic candidate are:
state prob now
WI 89R
IL 87R
IN 81R
NH 67R
PA 64R
NV 53Dpivot for 52 Democratic seats
NC 44R
MO 26R
FL 23R
AZ 20R
OH 15R
IA 11R
64 = PredictWise market-based probability of the Democrats controlling the Senate.

If the Democrats win Nevada and all the states above it, they will have 52 seats, counting the 2 independents as Democrats. If they win Pennslyvania and all the states above it but lose Nevada, they will have 50 seats. They will still control the Senate if they win the White House. According to the ranking assumption, the PredictWise market probablility that they control the Senate is thus 64 percent (the probablity they win Pennslyvania) if they win the White House and 53 percent (the probablility they win Nevada) if they don't. If we use the PredictWise market-based probabilty of 75 percent that Clinton wins the presidential electon, then the ranking assumption probability that the Democrats control the Senate is 0.75x64 + 0.25x53, which is 61 percent. This is close to the PredictWise market-based probability of the Democrats controlling the Senate of 64 percent.

Data collected from PredictWise on September 20, 2016

The current make up of the Senate is 54 Republicans and 46 Democrats, counting the 2 independents as Democrats. Only 10 states are in play in having market probabilities on the PredictWise website less than 90 percent and greater than 10 percent. The 10 states ranked by the market probabilities from PredictWise for the Democratic candidate are:

state prob now
WI 89R
IL 85R
IN 74R
PA 62R
NH 55R
NV 49Dpivot for 52 Democratic seats
NC 36R
MO 30R
FL 14R
OH 11R
54 = PredictWise market-based probability of the Democrats controlling the Senate.

If the Democrats win Nevada and all the states above it, they will have 52 seats, counting the 2 independents as Democrats. If they win New Hampshire and all the states above it but lose Nevada, they will have 50 seats. They will still control the Senate if they win the White House. According to the ranking assumption, the PredictWise market probablility that they control the Senate is thus 55 percent (the probablity they win New Hampshire) if they win the White House and 49 percent (the probablility they win Nevada) if they don't. If we use the PredictWise market-based probabilty of 72 percent that Clinton wins the presidential electon, then the ranking assumption probability that the Democrats control the Senate is 0.72x55 + 0.28x49, which is 53 percent. This is close to the PredictWise market-based probability of the Democrats controlling the Senate of 54 percent.

Data collected from PredictWise on October 4, 2016

The current make up of the Senate is 54 Republicans and 46 Democrats, counting the 2 independents as Democrats. Only 13 states are in play in having market probabilities on the PredictWise website less than 96 percent and greater than 9 percent. The 13 states ranked by the market probabilities from PredictWise for the Democratic candidate are:

state prob now
CO 95D
WI 95R
IL 89R
IN 82R
PA 74R
NH 69Rpivot for 51 Democratic seats
NC 52R
NV 51D
MO 31R
FL 14R
OH 11R
LA 11R
AZ 10R
62 = PredictWise market-based probability of the Democrats controlling the Senate.

If the Democrats win New Hampshire and all the states above it, they will have 51 seats, counting the 2 independents as Democrats. If they lose New Hampshire but win Pennslyvania and all the states above it, they will have 50 seats. In this case they will still control the Senate if they win the White House. According to the ranking assumption, the PredictWise market probablility that they control the Senate is thus 74 percent (the probablity they win Pennslyvania) if they win the White House and 69 percent (the probablility they win New Hampshire) if they don't. If we use the PredictWise market-based probabilty of 80 percent that Clinton wins the presidential electon, then the ranking assumption probability that the Democrats control the Senate is 0.80x74 + 0.20x69, which is 73 percent. This is higher than the PredictWise market-based probability of the Democrats controlling the Senate of 62 percent.

Data collected from PredictWise on October 25, 2016

The current make up of the Senate is 54 Republicans and 46 Democrats, counting the 2 independents as Democrats. Only 11 states are in play in having market probabilities on the PredictWise website less than 95 percent and greater than 10 percent. The 11 states ranked by the market probabilities from PredictWise for the Democratic candidate are:

state prob now
IL 92R
WI 88R
NV 74D
IN 71R
PA 67R
NH 63Rpivot for 51 Democratic seats
MO 59R
NC 47R
FL 24R
LA 13R
AZ 11R
79 = PredictWise market-based probability of the Democrats controlling the Senate.

If the Democrats win New Hampshire and all the states above it, they will have 51 seats, counting the 2 independents as Democrats. If they lose New Hampshire but win Pennslyvania and all the states above it, they will have 50 seats. In this case they will still control the Senate if they win the White House. According to the ranking assumption, the PredictWise market probablility that they control the Senate is thus 67 percent (the probablity they win Pennslyvania) if they win the White House and 63 percent (the probablility they win New Hampshire) if they don't. If we use the PredictWise market-based probabilty of 90 percent that Clinton wins the presidential electon, then the ranking assumption probability that the Democrats control the Senate is 0.90x67 + 0.10x63, which is 66.6 percent. This is considerably lower than the PredictWise market-based probability of the Democrats controlling the Senate of 79 percent.