Table 7
Simultaneous Poissons Model for Vehicle Fleet Ownership
Dependent variable: total vehicles owned and distribution among cars, SUVs, pickups, and vans
Beta
SE
t-stat
P-value
Vehicle price/income
–0.2213
0.0075
–29.40
0.000
Car
Constant
0.148
0.021
7.03
0.000
Household size
0.0699
0.0043
16.30
0.000
Population density
–0.1519
0.0081
–18.70
0.000
Income per HH member
0.02
0.0042
4.77
0.000
SUV
Constant
–2.8437
0.0553
–51.40
0.000
Household size
0.273
0.0118
23.10
0.000
Population density
–0.4526
0.0311
–14.60
0.000
Income per HH member
0.1899
0.0095
20.00
0.000
Pickup
Constant
–0.6725
0.0383
–17.60
0.000
Household size
0.0715
0.008
8.92
0.000
Population density
–0.9598
0.0281
–34.20
0.000
Income per HH member
–0.1102
0.0093
–11.80
0.000
Minivan
Constant
–3.1526
0.058
–54.30
0.000
Household size
0.4446
0.0103
43.00
0.000
Population density
–0.3993
0.0303
–13.20
0.000
Income per HH member
0.0262
0.0141
1.86
0.031
Log-likelihood function
Constant only
–89026.8
Convergence
–84399.8
Pseudo-R2
0.052
Number of observations: 32,596 households
Model form: Number of vehicles of type i owned ~ Poisson (λi ) with λi = exp(β′iXi) + βprice/income x Price/Income
