This limitation is addressed by applying an approach similar to the difference-in-differences method widely used to identify how the evolution of a given part of a system differs from the rest of the system if “treated” by an intervention (Angrist and Krueger 1999). In this case, the application of the method is aimed at identifying whether the typical shopping-purpose trip attractor zones within the urban area have had a different evolution of mobility demand for the HBO and NHB groups than other parts of the urban area. The origin-destination matrices identify trips by carriers (cab drivers, public transport drivers, urban goods distribution vehicles, etc.) in a grouped manner. Specifically, two groups of zones are defined:

- “Treatment” group, or areas that are considered to be shopping trip attractor zones and that are likely to have been impacted by the potential substitution effect created by the growth of e-commerce (the "treatment", in this context), such as areas in which a major shopping center is located, areas in which a major commercial center and adjacent areas are located, and areas that concentrate one-third of trips destined for shopping activities, according to the 2019 household mobility survey; and

- Comparison group, which includes other areas of the city.

A series of outcome metrics are defined and their evolution over time is calculated within the “treatment” and the comparison areas to subsequently compare the two, including, among others: number of trips during the morning (9:00-12:00) and the evening (19:00-20:00) shopping peak hours; and travel from areas inhabited by different income groups<sup>4</sup> to the two types of areas, in particular, focusing on the higher income groups that are known to have higher e-commerce adoption rates.

The CDR-based indicators were combined with complementary data, including, among others:

- For Bogota: E-commerce sales reports for Colombia; a tool developed by the Latin American Center for Logistics Innovation (CLI) that integrates order shipment data from three e-commerce companies in 2019; National Quality of Life Survey (ECV); Bogotá Household Mobility Survey 2019; and SDM Bogotá (2021) which includes interviews with 2,126  load generating and attracting establishments in Bogota in 20202021 and classified cargo vehicle traffic counts in Bogota in 2015 and October 2020.

- For Buenos Aires: E-commerce reports for Argentina produced by the Argentine Chamber of Electronic Commerce; e-commerce survey of AMBA consumers in 2020; National Household Expenditure Survey (2017-2018); classified traffic counts of freight vehicles in Buenos Aires in 2018-2019 collected by the Undersecretary of Mobility Planning of CABA; and the ENMODO household travel surveys for Buenos Aires (2008-2009, 2018-2020<sup>5</sup> ).

# **4. E-commerce-related mobility prior to the pandemic and potential for shopping trip elimination**

Trips linked to shopping activities in 2019 accounted for about 10.5 percent of total mobility in Bogotá on weekdays (EDM Bogota 2019). About 85 percent of shopping trips in 2019 were reported as home-based, i.e., originating from or destined for home. However, it should be noted that household surveys tend to underrepresent non-home-based trips and trips made for activities of short duration (Chapleau 2018) and overestimate the proportion of home-based trips due to response bias (Aschauer et al. 2018). Nearly 10 percent of all home-based trips, one-fifth of the home-based trips other than “compulsory mobility” (work, education), and 15 percent of non-home-based trips were for shopping purposes. About 25 percent of shopping trips in Bogota in 2019 were part of a trip chain, the percentage being much higher among non-home-

> 4 Income groups are approximated by the spatial classification of socioeconomic wellbeing used by the city planning agencies: in Bogota, according to the “strata” classification of city blocks, where 1 (low-low), 2 (low), 3 (low-medium), 4 (medium), 5 (medium-high), and 6 (high); in Buenos Aires, according to the share of unsatisfied basic needs (Necesidades Básicas Insatisfechas, or NBI) of the population inhabiting a city block (deciles) available from the National Institute of Statistics and Census of Argentina (INDEC) at the census radius level for most of the study area.

> 5 It includes a complete characterization of the trips in its sample, in particular, trips for shopping purposes.

6