Objective—To determine the association between licensing and registration of firearm sales and an indicator of gun availability to criminals. Methods—Tracing data on all crime guns recovered in 25 cities in the United States were used to estimate the relationship between state gun law categories and the proportion of crime guns first sold by in-state gun dealers. Results—In cities located in st...

Progressive cities worldwide have demonstrated political leadership by initiating meaningful strategies and actions to tackle climate change. However, the lack of knowledge concerning embodied greenhouse gas (GHG) emissions of cities has hampered effective mitigation. We analyse trans-boundary GHG emission transfers between five Australian cities and their trading partners, with embodied emissi...

As increasing urbanization has become a national policy priority for economic growth in China, cities have become important players in efforts to reduce carbon emissions. However, their efforts have been hampered by the lack of specific and comparable carbon emission inventories. Comprehensive carbon emission inventories for twelve Chinese cities, which present both a relatively current snapsho...

Net product entry is procyclical, which amplifies fluctuations in consumer welfare over the cycle if consumers have love for variety. Using barcode-level data covering grocery expenditures in 26 major cities, I establish that differences in city-level product entry are largely uncorrelated with local economic conditions. I provide evidence that city-level changes in product variety over the bus...

With urban population increasing dramatically worldwide, cities are playing an increasingly critical role in human societies and the sustainability of the planet. An obstacle to effective policy is the lack of meaningful urban metrics based on a quantitative understanding of cities. Typically, linear per capita indicators are used to characterize and rank cities. However, these implicitly ignor...