How did U.S. border crossing numbers change between 2016 and 2020 by month?
Executive summary
The monthly pattern of U.S. border crossings from 2016 through 2020 shows a familiar seasonal cycle around a multi-year decline after 2016 and then a sharp disruption in 2020 driven by COVID-19 and the Title 42 expulsions policy; official CBP "encounter" and BTS port-entry series report falling annual totals through 2019, routine seasonal peaks in late spring/early summer, and a marked drop in March–April 2020 followed by a gradual rebound later that year [1] [2] [3]. Data definitions shift in March 2020 when CBP began counting expulsions under the "encounters" umbrella, complicating direct month-to-month comparisons across that breakpoint [4] [2].
1. What the monthly numbers actually measure and why that matters
Monthly series commonly cited are not a single, consistent count: CBP "encounters" combine Border Patrol apprehensions, OFO inadmissibles and, starting March 2020, Title 42 expulsions, while the Bureau of Transportation Statistics reports traffic at ports of entry (vehicles, pedestrians, passengers) rather than unique people [5] [6]. That means month-to-month patterns reflect a mix of enforcement activity, migrant recidivism, seasonal travel and methodological changes that must be accounted for when interpreting trends [2] [6].
2. The 2016 baseline and seasonal rhythm
Fiscal‑year 2016 monthly apprehension tables published by CBP show the classic seasonal rhythm: lower counts in winter months, rising in spring and peaking in late spring/early summer—patterns replicated in Border Patrol monthly tables and BTS port-entry data for 2016 (CBP FY2016 monthly apprehensions source) [1] [6]. These monthly cycles formed the baseline against which subsequent years’ declines and disruptions were measured [1].
3. 2017–2019: a multi‑year decline with persistent seasonality
Across 2017–2019 the broad picture was declining annual unauthorized entries compared with the 2000s, with average unauthorized entries from 2013–2020 dropping to roughly 190,000 per year and CBP reporting higher apprehension rates in that period—yet monthly seasonality remained [2]. CBP and secondary summaries show lower total encounters in those years compared with earlier peaks, but the same winter trough / spring rise pattern persisted in monthly series reported by Border Patrol [2] [1].
4. 2020: pandemic shock, Title 42 and the monthly break in the series
The calendar year 2020 is a clear inflection: encounters dipped sharply between March and April 2020 as the Trump administration invoked Title 42 and COVID‑19 travel restrictions began; CBP began treating expulsions as encounters in March 2020, and encounter counts therefore reflect both fewer arrivals and a new processing category [2] [4]. After the initial March–April slump, encounter numbers gradually rebounded through the latter half of 2020 as seasonal patterns resumed and operational practices adjusted, but the inclusion of Title 42 expulsions inflated encounter counts relative to prior years because expelled individuals were more likely to attempt repeated crossings [2].
5. Putting month‑by‑month comparisons in perspective and data caveats
Direct month‑by‑month comparisons from 2016 through 2020 are feasible using CBP’s monthly apprehension tables and BTS port-entry downloads, but must be done with caution: the CBP definition of encounters changed in March 2020, BTS counts reflect crossings at ports not unique people, and encounter totals can double‑count repeat attempts by the same individuals—limitations noted by CBP and secondary analysts [4] [6] [2]. Public summaries therefore reliably describe the pattern—seasonal peaks in spring/early summer, a multi‑year decline from 2016 to 2019, and an abrupt pandemic‑era disturbance in March–April 2020 followed by a partial rebound—but generating a clean month‑by‑month table that is apples‑to‑apples across the whole 2016–2020 span requires downloading the original CBP monthly files and adjusting for the March 2020 definitional breakpoint [1] [5] [2].