How do fiscal-year versus calendar-year totals affect comparison of border crossing trends across administrations?
Executive summary
Comparing border crossing trends across administrations is sensitive to whether analysts use federal fiscal-year totals (Oct. 1–Sept. 30) or calendar-year totals, because the two systems slice migration flows at different points in time and mask seasonality, policy timing, repeat encounters and differing data definitions; reporters and political actors often choose the cadence that makes their favored narrative cleaner (Pew [1]; CBP p1_s5). Both fiscal-year and calendar-year series are legitimate, but each requires explicit caveats about how policy changes, data revisions and operational definitions align with the year boundaries being reported (CBP [2]; USAFacts p1_s4).
1. Why the choice of year matters: different cut-points for policy effects
Federal fiscal years begin in October, so a policy change announced or enacted in January (for example, an administration change on Jan. 20) will be split across two fiscal years and can look less or more effective depending on whether the analyst groups October–September totals or January–December totals; CBP emphasizes that final statistics are reported on a fiscal-year basis and routinely warns users about timing and revisions (CBP [2]; CBP nationwide encounters p1_s5). Analysts who want to show a rapid post-inauguration effect sometimes prefer calendar-year comparisons because they align two full January–December spans with presidential terms, while those stressing operational year-to-year trends in agency reporting commonly use fiscal years — which is also the basis for many official charts (Newsweek [3]; Pew p1_s1).
2. Seasonality and monthly spikes: how year boundaries can distort trends
Migration is highly seasonal and can spike or ebb in particular months; cutting a series in October slices through typical seasonal peaks or troughs and can make a single fiscal-year total appear artificially high or low versus a calendar-year total that captures a different mix of high- and low-months (Migration Policy [4]; Pew p1_s1). For example, analysts citing dramatic year-over-year swings frequently note December or September months as outliers; when those months land on opposite ends of fiscal years versus calendar years, year-to-year comparisons tell different stories even when underlying monthly behavior is unchanged (Migration Policy [1]1).
3. Repeat encounters and “encounters vs distinct people” caveat
CBP encounter totals count apprehensions, inadmissibles and expulsions and can include repeat crossers — a repeating individual can generate multiple encounters in a single year — so both fiscal and calendar totals overstate the count of distinct people if that distinction is not made clear (CBP [5]; Pew p1_s1). Pew and USAFacts highlight that a substantial share of encounters in recent years involved repeat crossers, meaning totals alone do not equal unique migrants; political claims that cite raw encounter totals without this qualification risk misleading comparisons across administrations (Pew [1]; USAFacts p1_s4).
4. Data definitions, preliminary releases and political framing
CBP and DHS issue preliminary monthly data and final fiscal-year totals later; political offices and committees routinely issue immediate statements interpreting preliminary October or November figures as proof points — for instance, DHS and CBP press releases have touted record-low October starts to a fiscal year as evidence of successful enforcement, whereas oversight committees have highlighted cumulative multi-year encounter totals to argue the opposite, illustrating how different selections (month, fiscal-year, nationwide vs southwest-only) are used to support competing narratives (DHS/CBP [6]; DHS [7]; House Homeland p1_s3). Users should therefore note whether figures are preliminary or final and exactly which encounter definitions are included (CBP [5]; CBP enforcement stats [1]3).
5. Best practices for fair, cross-administration comparison
To compare administrations responsibly, present both fiscal-year and calendar-year totals (or better, monthly time series) and explicitly state the year definition, whether counts are encounters or unique individuals, and whether data are preliminary or final; supplement totals with measures of seasonality and repeat crossers and cite CBP’s data portal and methodology notes so readers can replicate the math (CBP nationwide encounters [5]; CBP Southwest encounters [2]; Pew p1_s1). Where available, triangulate with non-CBP sources such as Migration Policy or BTS to check port-of-entry versus between-port metrics, and flag partisan sources (DHS press releases and committee factsheets) that may emphasize selective slices of the data for political effect (Migration Policy [4]; BTS [8]; DHS/Homeland [7]; House Homeland p1_s3).