Are Difference-in-Differences Estimates Blowing Smoke? A Cautionary Tale From an Oft-Used Natural Experiment

2021 ◽  
Author(s):  
Anthony Zdrojewski ◽  
Alexander W. Butler
Keyword(s):  
Natural Experiment ◽  
Cautionary Tale ◽  
Difference In Differences

scholarly journals Impact of banning smoking in cars with children on exposure to second-hand smoke: a natural experiment in England and Scotland

2019 ◽  
Author(s):  
Anthony A Laverty ◽  
Thomas Hone ◽  
Philip E. Anyanwu ◽  
David Taylor Robinson ◽  
Frank de Vocht ◽  
...  
Keyword(s):  
Logistic Regression ◽  
Survey Data ◽  
Tobacco Smoke ◽  
Natural Experiment ◽  
Second Hand Smoke ◽  
Regression Analyses ◽  
Difference In Difference ◽  
Difference In Differences ◽  
Survey Weighting ◽  
The Impact

ABSTRACTA ban on smoking in cars with children was implemented in April 2015 in England and December 2016 in Scotland. With survey data from both countries (NEngland=3,483-6,920 and NScotland=232-319), we used this natural experiment to assess the impact of the ban using a difference-in-differences approach. We conducted logistic regression analyses within a Difference-in-Difference framework and adjusted for age, sex, a marker of deprivation and survey weighting for non-response. Among children aged 13-15 years, self-reported levels of regular exposure to smoke in cars were 3.4% in 2012, 2.2% in 2014 and 1.3% in 2016 for Scotland and 6.3%, 5.9% and 1.6% in England. The ban was associated with a 73% reduction (95%CI -59%, -81%) in self-reported exposure to tobacco smoke among children.

scholarly journals The Buck Stops Where? Federalism, Uncertainty, and Investment in the Brazilian Water and Sanitation Sector

2020 ◽  
Vol 12 (3) ◽  
pp. 374-401 ◽  
Author(s):  
Evan Plous Kresch
Keyword(s):  
Public Service ◽  
Service Provision ◽  
Natural Experiment ◽  
Total System ◽  
Difference In Differences ◽  
Water And Sanitation ◽  
Regulatory Uncertainty ◽  
System Access ◽  
The Relationship ◽  
Different Levels

This paper documents how regulatory uncertainty may undermine public service when different levels of government share a mandate on public service provision. I examine the Brazilian water and sanitation sector, which presents a natural experiment of shared provision between state and municipal companies. Using a difference-in-differences framework, I study a legal reform that clarified the relationship between municipal and state providers and eliminated any takeover threat by state companies. I find that after the reform, municipal companies almost doubled their total system investment, leading to significant increases in system access and decreases in child mortality. (JEL H77, L95, O13, O18, Q53)

scholarly journals Is a Regional Coordination Approach to Air Pollution Management Helpful? Evidence from China

2019 ◽  
Vol 12 (1) ◽  
pp. 134 ◽  
Author(s):  
Xuehui Zhang ◽  
Zhidong Tan ◽  
Bao-Guang Chang ◽  
Kam C. Chan
Keyword(s):  
Air Pollution ◽  
Natural Experiment ◽  
Active Role ◽  
Difference In Differences ◽  
Administrative Management ◽  
New Methods ◽  
Regional Coordination ◽  
Pollution Management ◽  
Local Officials ◽  
The Government

In February 2017 China began to require the regional coordination of four ministries and 28 cities surrounding Beijing to manage air pollution. The Coordination attempts to unify air pollution standards and implements various new methods to monitor air pollution. Leveraging the natural experiment and using a difference-in-differences research design, we note that firms located in the treatment cities invest more in the environment than those in the control cities. In addition, we find that non-state-owned firms (non-SOEs) respond more strongly than SOEs. The findings remain qualitatively the same after accounting for selection bias in the cities included in the Coordination. Most importantly, air quality improves for treatment cities after the implementation of the Coordination. Our findings offer lessons to other emerging markets for implementing their air pollution management programs. Specifically, we sharpen our knowledge of the administrative management needed to improve coordination among government agencies and local officials in the management of air pollution and suggest that the government can play an active role in enhancing air pollution management.

scholarly journals Bismarck’s Health Insurance and the Mortality Decline

2019 ◽  
Vol 18 (5) ◽  
pp. 2561-2607 ◽  
Author(s):  
Stefan Bauernschuster ◽  
Anastasia Driva ◽  
Erik Hornung
Keyword(s):  
Health Insurance ◽  
Fixed Effects ◽  
Natural Experiment ◽  
Social Health Insurance ◽  
Insurance Fund ◽  
Difference In Differences ◽  
German Empire ◽  
Compulsory Health Insurance ◽  
The Impact ◽  
Significant Mortality

Abstract We study the impact of social health insurance on mortality. Using the introduction of compulsory health insurance in the German Empire in 1884 as a natural experiment, we estimate difference-in-differences and regional fixed effects models exploiting variation in eligibility for insurance across occupations. Our findings suggest that Bismarck’s health insurance generated a significant mortality reduction. Despite the absence of antibiotics and most vaccines, we find the results to be largely driven by a decline of deaths from infectious diseases. Further evidence suggests that statutory access to well-trained doctors was an elementary channel. This finding may be explained by insurance fund physicians transmitting new knowledge on infectious disease prevention.

scholarly journals Ecological Civilization Demonstration Zone, Air Pollution Reduction, and Political Promotion Tournament in China: Empirical Evidence from a Quasi-Natural Experiment

2021 ◽  
Vol 18 (22) ◽  
pp. 11880
Author(s):  
Haijie Wang ◽  
Yong Geng ◽  
Jingxue Zhang ◽  
Xiqiang Xia ◽  
Yanchao Feng
Keyword(s):  
Air Pollution ◽  
Natural Experiment ◽  
Spillover Effects ◽  
Pollution Reduction ◽  
The Political ◽  
Ecological Civilization ◽  
Difference In Differences ◽  
Binary Logit ◽  
The Difference ◽  
Promotion Tournament

Using the ecological civilization demonstration zone as a quasi-natural experiment, this study has explored the effect of it on air pollution in China by employing the difference-in-differences model and the spatial difference-in-differences model, and further tested the political promotion tournament in China by employing the binary logit model. The results show that the ecological civilization demonstration zone has basically and effectively reduced air pollution, except for carbon monoxide and ozone. In addition, the spatial spillover effects of the ecological civilization demonstration zone on air pollution are not only basically supported among the treated cities, but also extremely established in the untreated cities neighboring the treated cities. Furthermore, no clear evidence supports the establishment of the political promotion tournament in China, while local cadres tend to cope with the assessment of higher officials passively rather than actively. Overall, this study sheds light on the coordination of economic development and ecological civilization from the perspective of the career concerns of local cadres.

scholarly journals Impact of a nighttime curfew on overnight mobility

2021 ◽  
Author(s):  
Amir Ghasemi ◽  
Nick Daneman ◽  
Isha Berry ◽  
Sarah A Buchan ◽  
Jean-Paul Soucy ◽  
...  
Keyword(s):  
Urban Areas ◽  
Natural Experiment ◽  
Substantial Decrease ◽  
Relative Reduction ◽  
Difference In Differences ◽  
Second Wave ◽  
Pharmaceutical Interventions

Background: Among non-pharmaceutical interventions, individual movement restrictions have been among the most impactful methods for controlling COVID-19 case growth. While nighttime curfews to control COVID-19 case growth have been implemented in certain regions and cities, few studies have examined their impacts on mobility or COVID-19 incidence. In the second wave of COVID-19, Canada's two largest and adjacent provinces implemented lockdown restrictions with (Quebec) and without (Ontario) a nighttime curfew, providing a natural experiment to study the association between curfews and mobility. Methods: This study spanned from December 1, 2020 to January 23, 2021 and included the populations of Ontario (including Toronto) and Quebec (including Montreal). The intervention of interest was a nighttime curfew implemented across Quebec on January 9, 2021. Unadjusted and adjusted difference-in-differences models (DID) were used to measure the incremental impact of the curfew on nighttime mobility in Quebec as compared to Ontario. Results: The implementation of the curfew was associated with an immediate reduction in nighttime mobility. The adjusted DID analysis indicated that Quebec experienced a 31% relative reduction in nighttime mobility (95%CI: -36% to -25%) compared to Ontario, and that Montreal experienced a 39% relative reduction compared to Toronto (95%CI: -43, -34). Discussion: However, this natural experiment among two neighbouring provinces provides useful evidence that curfews lead to an immediate and substantial decrease nighttime mobility, particularly in these provinces' largest urban areas hardest hit by COVID-19.

scholarly journals Increasing Block Rate Electricity Pricing and Propensity to Purchase Electrical Appliances: Evidence from a Natural Experiment in Russia

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6954
Author(s):  
Salim Turdaliev
Keyword(s):  
Panel Data ◽  
Empirical Evidence ◽  
Natural Experiment ◽  
Electricity Pricing ◽  
Energy Policies ◽  
Difference In Differences ◽  
Household Level ◽  
Percentage Points ◽  
Residential Electricity ◽  
The Relationship

This paper provides empirical evidence on the relationship between the increasing-block-rate (IBR) pricing of electricity and the propensity of households to buy major electrical appliances. I use a variation from a natural experiment in Russia that introduced IBR pricing for residential electricity in a number of experimental regions in 2013. The study employs household-level panel data, which records, among others, whether the household has purchased any major electrical appliances during the last three months. Using a difference-in-differences specification, I show that the purchase of major electrical appliances in the regions with IBR pricing has increased by more than 20% (or more than two percentage points). The findings suggest that price-based energy policies may be an effective tool in shaping the behaviour of households.

scholarly journals Impact of banning smoking in cars with children on exposure to second-hand smoke: a natural experiment in England and Scotland

Thorax ◽  
2020 ◽  
Vol 75 (4) ◽  
pp. 345-347 ◽  
Author(s):  
Anthony A Laverty ◽  
Thomas Hone ◽  
Eszter P Vamos ◽  
Philip E Anyanwu ◽  
David Taylor-Robinson ◽  
...  
Keyword(s):  
Logistic Regression ◽  
Survey Data ◽  
Tobacco Smoke ◽  
Natural Experiment ◽  
Second Hand Smoke ◽  
Relative Reduction ◽  
Difference In Differences ◽  
Absolute Reduction

England banned smoking in cars carrying children in 2015 and Scotland in 2016. We used survey data from 3 years for both countries (NEngland=3483–6920, NScotland=232–319) to assess effects of the English ban using logistic regression within a difference-in-differences framework. Among children aged 13–15 years, self-reported levels of regular exposure to smoke in cars for Scotland were 3.4% in 2012, 2.2% in 2014 and 1.3% in 2016 and for England 6.3%, 5.9% and 1.6%. The ban in England was associated with a −4.1% (95% CI −4.9% to −3.3%) absolute reduction (72% relative reduction) in exposure to tobacco smoke among children.

scholarly journals Of Mice and Academics: Examining the Effect of Openness on Innovation

2016 ◽  
Vol 8 (1) ◽  
pp. 212-252 ◽  
Author(s):  
Fiona Murray ◽  
Philippe Aghion ◽  
Mathias Dewatripont ◽  
Julian Kolev ◽  
Scott Stern
Keyword(s):  
Intellectual Property ◽  
Late Stage ◽  
Natural Experiment ◽  
Research Output ◽  
Genetically Engineered ◽  
Difference In Differences ◽  
Research Directions ◽  
Genetically Engineered Mice ◽  
The Creation

This paper argues that openness, by lowering costs to access existing research, can enhance both early and late stage innovation through greater exploration of novel research directions. We examine a natural experiment in openness: late-1990s NIH agreements that reduced academics’ access costs regarding certain genetically engineered mice. Implementing difference-in-differences estimators, we find that increased openness encourages entry by new researchers and exploration of more diverse research paths, and does not reduce the creation of new genetically engineered mice. Our findings highlight a neglected cost of strong intellectual property restrictions: lower levels of exploration leading to reduced diversity of research output. (JEL I23, O31, O33, O34)

Gender Discrimination in Exam Grading? Double Evidence from a Natural Experiment and a Field Experiment

2019 ◽  
Vol 19 (2) ◽  
Author(s):  
Beatrice Schindler Rangvid
Keyword(s):  
Field Experiment ◽  
Gender Discrimination ◽  
Natural Experiment ◽  
Causal Effect ◽  
Difference In Differences ◽  
Full Cohort ◽  
Gender Biases

Abstract Grading bias against boys may be one of the reasons why boys underperform in school compared to girls. This study assesses the causal effect of blind grading of boys relative to girls using difference-in-differences methods and exploiting two separate identification strategies: a unique full cohort natural experiment providing exogenous variation in blind grading, and a field experiment where the exact same exam papers are scored twice (blind and non-blind). Even though the two strategies hinge on different assumptions, the results persistently suggest against the existence of systematic gender biases in non-blind evaluation. The results are robust to different model specifications.

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