Table 4. Open in new tab Effect of...

	All hours	Morning peak	Evening peak	Off-peak	Weekends
(a) Specifications with economic variables
With gasoline prices	0.128	0.046	0.088	0.106	0.052
	(0.117)	(0.066)	(0.129)	(0.172)	(0.094)
With real exchange rate	0.095	0.136	0.092	0.051	0.054
	(0.099)	(0.090)	(0.125)	(0.133)	(0.099)
(b) Specifications with other controls
With industrial prod. index	0.173	0.127	0.147	0.158	0.057
	(0.152)	(0.080)	(0.170)	(0.202)	(0.092)
With SO₂	0.168	0.066	0.158	0.159	−0.038
	(0.145)	(0.071)	(0.159)	(0.195)	(0.090)
With technology regulation	0.182	0.128*	0.153	0.171	0.061
	(0.148)	(0.076)	(0.164)	(0.200)	(0.095)
With roadwork investment	0.184	0.130*	0.156	0.174	0.063
	(0.150)	(0.076)	(0.165)	(0.203)	(0.095)
(c) Alternative polynomial orders
6th-order polynomial	0.152	0.110*	0.128	0.134	0.081
	(0.114)	(0.065)	(0.126)	(0.157)	(0.093)
7th-order polynomial	0.100	0.039	0.058	0.041	0.118
	(0.112)	(0.082)	(0.125)	(0.149)	(0.103)
Weather quartics	0.168	0.120*	0.135	0.152	0.025
	(0.143)	(0.072)	(0.171)	(0.201)	(0.098)
(d) Specifications with orthogonal regressors
With principal components	0.168	0.072	0.142	0.211	0.049
	(0.140)	(0.084)	(0.166)	(0.167)	(0.125)

All hours

Morning peak

Evening peak

Off-peak

Weekends

(1)

(2)

(3)

(4)

(5)

(a) Specifications with economic variables

With gasoline prices

0.128

0.046

0.088

0.106

0.052

(0.117)

(0.066)

(0.129)

(0.172)

(0.094)

With real exchange rate

0.095

0.136

0.092

0.051

0.054

(0.099)

(0.090)

(0.125)

(0.133)

(0.099)

(b) Specifications with other controls

With industrial prod. index

0.173

0.127

0.147

0.158

0.057

(0.152)

(0.080)

(0.170)

(0.202)

(0.092)

With SO₂

0.168

0.066

0.158

0.159

−0.038

(0.145)

(0.071)

(0.159)

(0.195)

(0.090)

With technology regulation

0.182

0.128*

0.153

0.171

0.061

(0.148)

(0.076)

(0.164)

(0.200)

(0.095)

With roadwork investment

0.184

0.130*

0.156

0.174

0.063

(0.150)

(0.076)

(0.165)

(0.203)

(0.095)

(c) Alternative polynomial orders

6th-order polynomial

0.152

0.110*

0.128

0.134

0.081

(0.114)

(0.065)

(0.126)

(0.157)

(0.093)

7th-order polynomial

0.100

0.039

0.058

0.041

0.118

(0.112)

(0.082)

(0.125)

(0.149)

(0.103)

Weather quartics

0.168

0.120*

0.135

0.152

0.025

(0.143)

(0.072)

(0.171)

(0.201)

(0.098)

(d) Specifications with orthogonal regressors

With principal components

0.168

0.072

0.142

0.211

0.049

(0.140)

(0.084)

(0.166)

(0.167)

(0.125)

	All hours	Morning peak	Evening peak	Off-peak	Weekends
(a) Specifications with economic variables
With gasoline prices	0.128	0.046	0.088	0.106	0.052
	(0.117)	(0.066)	(0.129)	(0.172)	(0.094)
With real exchange rate	0.095	0.136	0.092	0.051	0.054
	(0.099)	(0.090)	(0.125)	(0.133)	(0.099)
(b) Specifications with other controls
With industrial prod. index	0.173	0.127	0.147	0.158	0.057
	(0.152)	(0.080)	(0.170)	(0.202)	(0.092)
With SO₂	0.168	0.066	0.158	0.159	−0.038
	(0.145)	(0.071)	(0.159)	(0.195)	(0.090)
With technology regulation	0.182	0.128*	0.153	0.171	0.061
	(0.148)	(0.076)	(0.164)	(0.200)	(0.095)
With roadwork investment	0.184	0.130*	0.156	0.174	0.063
	(0.150)	(0.076)	(0.165)	(0.203)	(0.095)
(c) Alternative polynomial orders
6th-order polynomial	0.152	0.110*	0.128	0.134	0.081
	(0.114)	(0.065)	(0.126)	(0.157)	(0.093)
7th-order polynomial	0.100	0.039	0.058	0.041	0.118
	(0.112)	(0.082)	(0.125)	(0.149)	(0.103)
Weather quartics	0.168	0.120*	0.135	0.152	0.025
	(0.143)	(0.072)	(0.171)	(0.201)	(0.098)
(d) Specifications with orthogonal regressors
With principal components	0.168	0.072	0.142	0.211	0.049
	(0.140)	(0.084)	(0.166)	(0.167)	(0.125)

Table 4.

Open in new tab

Effect of Drastic Restriction on CO Concentration: Robustness Checks

	All hours	Morning peak	Evening peak	Off-peak	Weekends
	(1)	(2)	(3)	(4)	(5)
(a) Specifications with economic variables
With gasoline prices	0.128	0.046	0.088	0.106	0.052
	(0.117)	(0.066)	(0.129)	(0.172)	(0.094)
With real exchange rate	0.095	0.136	0.092	0.051	0.054
	(0.099)	(0.090)	(0.125)	(0.133)	(0.099)
(b) Specifications with other controls
With industrial prod. index	0.173	0.127	0.147	0.158	0.057
	(0.152)	(0.080)	(0.170)	(0.202)	(0.092)
With SO₂	0.168	0.066	0.158	0.159	−0.038
	(0.145)	(0.071)	(0.159)	(0.195)	(0.090)
With technology regulation	0.182	0.128*	0.153	0.171	0.061
	(0.148)	(0.076)	(0.164)	(0.200)	(0.095)
With roadwork investment	0.184	0.130*	0.156	0.174	0.063
	(0.150)	(0.076)	(0.165)	(0.203)	(0.095)
(c) Alternative polynomial orders
6th-order polynomial	0.152	0.110*	0.128	0.134	0.081
	(0.114)	(0.065)	(0.126)	(0.157)	(0.093)
7th-order polynomial	0.100	0.039	0.058	0.041	0.118
	(0.112)	(0.082)	(0.125)	(0.149)	(0.103)
Weather quartics	0.168	0.120*	0.135	0.152	0.025
	(0.143)	(0.072)	(0.171)	(0.201)	(0.098)
(d) Specifications with orthogonal regressors
With principal components	0.168	0.072	0.142	0.211	0.049
	(0.140)	(0.084)	(0.166)	(0.167)	(0.125)

	All hours	Morning peak	Evening peak	Off-peak	Weekends
	(1)	(2)	(3)	(4)	(5)
(a) Specifications with economic variables
With gasoline prices	0.128	0.046	0.088	0.106	0.052
	(0.117)	(0.066)	(0.129)	(0.172)	(0.094)
With real exchange rate	0.095	0.136	0.092	0.051	0.054
	(0.099)	(0.090)	(0.125)	(0.133)	(0.099)
(b) Specifications with other controls
With industrial prod. index	0.173	0.127	0.147	0.158	0.057
	(0.152)	(0.080)	(0.170)	(0.202)	(0.092)
With SO₂	0.168	0.066	0.158	0.159	−0.038
	(0.145)	(0.071)	(0.159)	(0.195)	(0.090)
With technology regulation	0.182	0.128*	0.153	0.171	0.061
	(0.148)	(0.076)	(0.164)	(0.200)	(0.095)
With roadwork investment	0.184	0.130*	0.156	0.174	0.063
	(0.150)	(0.076)	(0.165)	(0.203)	(0.095)
(c) Alternative polynomial orders
6th-order polynomial	0.152	0.110*	0.128	0.134	0.081
	(0.114)	(0.065)	(0.126)	(0.157)	(0.093)
7th-order polynomial	0.100	0.039	0.058	0.041	0.118
	(0.112)	(0.082)	(0.125)	(0.149)	(0.103)
Weather quartics	0.168	0.120*	0.135	0.152	0.025
	(0.143)	(0.072)	(0.171)	(0.201)	(0.098)
(d) Specifications with orthogonal regressors
With principal components	0.168	0.072	0.142	0.211	0.049
	(0.140)	(0.084)	(0.166)	(0.167)	(0.125)

Source: Data from RMCAB. Author’s calculations.

Notes: This table shows PYP estimates from 50 regressions for the drastic phase. Each estimate reports the PYP coefficient of an alternative specification. The dependent variable is carbon monoxide (CO) in logs. All specifications are fitted along a polynomial time trend of degree five (except for the first two models in panel (c)) and include meteorological variables and indicator variables for month of the year, day of the week, and hour of the day. Interactions between weekends and hour of the day are added only in the “all hours” model. Standard errors, in parentheses, are robust to heteroscedasticity and arbitrary correlation within one-week clusters. Estimates marked

*p < 0.10.

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