1. What do the results of Table 4 suggest about the effects of helmet laws on helmet use for adults and for youths?2. Discuss the results of Table 6 concerning heterogeneity in the effects of allage helmet laws on both youths and adults.
Instructions ECON7012/8012 – Topic 5a Evaluating outcomes from policy reform A/Prof Jordi McKenzie, Department of Economics Paper Details • Carpenter, C. S., & Warman, C. (2019), ‘What do bicycle helmet laws do? Evidence from Canada’, Economic Inquiry, 57(2), 832-854. Abstract Twenty-one states and the District of Columbia require youths to wear helmets when riding a bicycle, and there has been a push to extend such laws to adults. We provide new evidence on helmet laws by studying Canada using difference-in-differences models and restricted area-identified public health survey data with information on cycling and helmet use for nearly 800,000 individuals from 1994 to 2014. We first confirm prior patterns from the United States that laws requiring youths to wear helmets significantly increased youth helmet use. We then provide the literature’s first comprehensive evidence that “all-age” bicycle helmet laws significantly increased both adult and youth helmet use by 50%–190% relative to pre-reform levels, with larger effects for younger adults and less-educated adults. All-age helmet laws had modest effects at reducing cycling and increasing in-home exercise during winter months among adults but did not meaningfully affect weight. Overall, our findings confirm that all-age helmet laws can be effective at increasing population helmet use without significant unintended adverse health consequences. Introduction • Cycling accounts for largest number of head injuries in emergency rooms • Governments have increasingly adopted laws requiring children to wear helmets when riding a bicycle • Previous research using staggered timing of adoption of mandatory youth helmet laws across U.S. states has shown these laws had robust effects at reducing bicycle related deaths and injuries among youths ― However, this occurred not only through significantly greater helmet wearing but also through reduced bicycling participation Introduction • Local and state governments in the United States have debated extending helmet laws to apply to all individuals, including adults • The “all-age” helmet laws have been met with strong opposition from cycling activists, and thus far have not been adopted by any U.S. state ― Handful of places outside US have adopted them, including Australia and New Zealand • As public bike-share programs proliferate, there is concern that policies requiring adults to wear helmets would substantially limit their popularity and effectiveness Preview of Results • This paper provide quasi-experimental evidence on the effects of bicycle helmet laws by examining Canada where many provinces have adopted these policies over the past two decades ― The large samples of survey data (over 775,000 respondents) allow test for treatment effect heterogeneity • Use the staggered timing of adoption of the provincial helmet laws to estimate difference-in-differences models of the effects of laws on outcomes • Use two-way fixed effects models with controls for province and year fixed effects, individual characteristics, and other relevant public policies • Confirm prior research that youth-targeted helmet laws in Canada were associated with at most modest estimated declines in youth cycling and extremely large increases in youth helmet use Preview of Results • Examine all-age helmet laws and find no relationship with youth cycling • All-age helmet laws did, however, significantly increase youth helmet use by around 30 percentage points or nearly 200% • Find all-age helmet laws unrelated to adult cycling participation or intensity • Also find all-age helmet laws significantly increased probability that adults report always wearing helmets by around 19.7–24 percentage points, or about 50–65% relative to the average helmet use prior to adoption • Finally, also examine helmet law effects on other exercise behaviors ― Evidence that during winter months in Canada all-age helmet laws are associated with reductions in cycling and substitution toward in-home exercise Institutional Background • Laws generally require individuals to wear a helmet when cycling on public roads • Table 1 provides a list of the provinces and cities in Canada that adopted different types of helmet laws • Use two data sources to estimate the effects of mandatory helmet laws on helmet use and bicycle riding behaviour ― First data are restricted-use versions of the NPHS from 1994 to 1999 ― Second data from the CCHS from 2000 to 2014 • The NPHS and CCHS contain several questions about helmet use, bicycle riding, and other types of exercise used to create key outcome variables Data Description and Research Design • Create two bicycling outcomes based on these questions ― Any Past 3 Month Cycling. Indicator variable equals one if respondent reported any leisure cycling in past 3 months (and zero otherwise) ― Total # Minutes Leisure Cycling Past 3 Months. Combine information from questions about the number of times of leisure cycling and length of cycling on each occasion (using midpoints of ranges and assigning a value of 1.5 hours to respondents who say they cycle for more than an hour on each occasion) to create variable representing cycling intensity Data Description and Research Design • Also create two helmet use outcomes based on responses to question about frequency of helmet use ― Frequent Helmet Use. Equals one if the respondent reported wearing a helmet “always” or “most of the time” when riding a bicycle (and zero otherwise) ― Always Helmet Use. Equals one if the respondent reported always wearing a helmet (and zero otherwise) • The CCHS and NPHS data also allow direct measures of possible unintended adverse consequences of mandatory helmet laws, as prior work has found that youth helmet laws reduced youth cycling in the United States • In addition to cycling outcomes, also examine other exercise, weight, and obesity outcomes as further tests of possible unintended consequences Data Description and Research Design • Estimate two-way fixed effects models separately for youths and for adults ― Yipt are outcomes of interest for individual i in province p in year t ― Xipt is vector of individual characteristics that includes age, sex, race, education, and marital status ― Zpt is vector of province/time-varying covariates including the provincial unemployment rate and an indicator for whether the individual lives in a place that adopted a public bike-share program such and when a provincial graduated license policy came into effect ― Pp and Tt are full sets of province and year dummies, respectively Data Description and Research Design Results – Descriptive Patterns Results – Descriptive Patterns Descriptive Statistics Provincial Trends in Bicycling Participation Provincial Trends in Helmet Use Empirical Results Empirical Results Robustness Checks Heterogeneity Effects Exercise Participation Exercise Substitution Effects Discussion and Conclusion • Results show that bicycle helmet laws in Canada worked to significantly increase helmet use for both youths and adults • Youth-targeted laws significantly increased youth helmet use and all-age laws significantly increased both youth and adult helmet use ― In proportional terms effects of helmet laws at increasing youth helmet use were larger for all-age laws than for youth-targeted laws • Find little systematic evidence that all-age helmet laws in Canada induced population-wide reductions in cycling • Also find limited effects on other leisure-related physical activities, and do not find adverse effects on population weight Questions for Class Discussion 1. Explain how the ‘percentage effect’ is calculated for the all-age and youth law results in the various specification reported in Table 3. Are these results significant? 2. What do the results of Table 4 suggest about the effects of helmet laws on helmet use for adults and for youths? 3. Discuss the results of Table 6 concerning heterogeneity in the effects of all- age helmet laws on both youths and adults. 4. Highlight and discuss the main results about substitute exercise participation and seasonal exercise participation as presented in Tables 7 and 8. ECON7012/8012 – Topic 5a�Evaluating outcomes from policy reform Paper Details Introduction Introduction Preview of Results Preview of Results Institutional Background Slide Number 8 Slide Number 9 Slide Number 10 Slide Number 11 Results – Descriptive Patterns Results – Descriptive Patterns Descriptive Statistics Provincial Trends in Bicycling Participation Provincial Trends in Helmet Use Empirical Results Empirical Results Robustness Checks Heterogeneity Effects Exercise Participation Exercise Substitution Effects Discussion and Conclusion Questions for Class Discussion What Do Bicycle Helmet Laws Do? Evidence from Canada WHAT DO BICYCLE HELMET LAWS DO? EVIDENCE FROM CANADA CHRISTOPHER S. CARPENTER and CASEY WARMAN∗ Twenty-one states and the District of Columbia require youths to wear helmets when riding a bicycle, and there has been a push to extend such laws to adults. We provide new evidence on helmet laws by studying Canada using difference-in-differences models and restricted area-identified public health survey data with information on cycling and helmet use for nearly 800,000 individuals from 1994 to 2014. We first confirm prior patterns from the United States that laws requiring youths to wear helmets significantly increased youth helmet use. We then provide the literature’s first comprehensive evidence that “all-age” bicycle helmet laws significantly increased both adult and youth helmet use by 50%–190% relative to pre-reform levels, with larger effects for younger adults and less-educated adults. All-age helmet laws had modest effects at reducing cycling and increasing in-home exercise during winter months among adults but did not meaningfully affect weight. Overall, our findings confirm that all-age helmet laws can be effective at increasing population helmet use without significant unintended adverse health consequences. (JEL I18, I12, K32) I. INTRODUCTION Bicycling is enjoyed by over 66 million adults in the United States (Statista 2018) but is also associated with substantial health risks: according to the American Association of ∗The authors are grateful to Mark Anderson and three anonymous referees as well as Hope Corman and seminar participants at the 2018 NBER Spring Health Economics Program meeting, the Canadian Economic Association, the Southern Economic Association, Dalhousie University, Geor- gia State University, McMaster University, St. Francis Xavier University, and Saint Mary’s University for very valuable comments. The results in this paper are based on confiden- tial versions of the National Population Health Surveys and the Canadian Community Health Surveys. Readers interested in obtaining access can contact the authors for directions. The analysis presented in this paper was mainly conducted at the Atlantic Research Data Centre which is part of the Cana- dian Research Data Centre Network (CRDCN). The services and activities provided by the Atlantic Research Data Centre are made possible by the financial or in-kind support of the SSHRC, the CIHR, the CFI, Statistics Canada, and Dalhousie University. The views expressed in this paper do not necessar- ily represent the CRDCN or those of its partners. The authors are also grateful to RDC analyst Heather Hobson for her assis- tance, as well as Yasmine Amirkhalkhali and Min Hu. The authors also mention that all errors are their own. The usual caveats apply. Carpenter: Professor, Department of Economics, Vander- bilt University, NBER, and IZA, Nashville, TN 37240. Phone 615-322-0174, Fax 615-343-8495, E-mail christo-
[email protected] Warman: Associate Professor, Department of Economics, Dalhousie University and NBER, Halifax, NS B3H4R2, Canada. Phone 902-494-4252, Fax 902-494-6917, E-mail
[email protected] Neurological Surgeons, cycling is the sport