The Economics of Speed: The Electrification of the Streetcar System and the Decline of Mom-and-Pop Stores in Boston, 1885–1905
利用波士顿有轨电车电气化（1889-1896）这一自然实验，研究发现电气化后铁路沿线食品零售/批发店中个体户占比显著下降，表明城市交通改善通过扩大市场范围削弱了小商店的生存空间。
Small firms dominated the American economy in the nineteenth century, and they still dominate in many developing economies today. This paper tests whether geographic market segmentation due to underdeveloped intracity transportation technology precludes the emergence of large retail/wholesale stores. I exploit the natural experiment of Boston’s rapid electrification from its previous horse-drawn streetcar system, which occurred between 1889 and 1896. Analyzing newly digitized data, I find that rail-connected locations experienced a sharp decline in the share of sole proprietorships among food retail/wholesale establishments after the electrification relative to off-rail locations. Changes in market access due to streetcar electrification can explain this effect.