Munford Luke A
Manchester Centre for Health Economics, University of Manchester, UK.
Transp Res Part A Policy Pract. 2017 Mar;97:192-208. doi: 10.1016/j.tra.2017.01.018.
We analyse a new data set to examine how congestion charging policies affect an individual's investment social capital. We exploit a (quasi-) natural experiment - the implementation of the Western Extension Zone (WEZ) to the London Congestion Charging zone in 2007. We measure investment in social capital by using the frequency of visits to friends and family before and after the implementation of the WEZ. Using longitudinal data collected in January and November 2007 made available by Transport for London, we perform difference-in-difference analysis, using both OLS and interval regression, with the treatment group defined as those who used a car to make visits pre-WEZ. We observe large and statistically significant reductions in visits as a result of the WEZ, with, for example, a reduction of around 20 visits a year to friends. The effect of the WEZ on the number of visits to act as an informal carer is much larger, with reductions of around 100 visits a year. Given that the changes occurred in such a small time frame (10 months), we conclude that the WEZ is likely to be the main driver of these reductions.
我们分析了一个新的数据集，以研究拥堵收费政策如何影响个人对社会资本的投入。我们利用了一个（准）自然实验——2007年伦敦拥堵收费区西部扩展区（WEZ）的实施。我们通过测量WEZ实施前后拜访朋友和家人的频率来衡量对社会资本的投入。利用伦敦交通局提供的2007年1月和11月收集的纵向数据，我们采用OLS和区间回归进行双重差分分析，将处理组定义为在WEZ实施前开车拜访的人群。我们观察到，由于WEZ的实施，拜访次数大幅减少且具有统计学意义，例如，每年拜访朋友的次数减少了约20次。WEZ对作为非正式护理人员的拜访次数的影响要大得多，每年减少约100次。鉴于这些变化发生在如此短的时间内（10个月），我们得出结论，WEZ可能是这些减少的主要驱动因素。
