apprehended migrants—a situation that appears to have been more common in the early 2000s, when the ratio of apprehensions to USBP officers was much higher than today. Currently a USBP station needs the approval of its station chief to forego fingerprinting and interviewing a subject. USBP asserts that it enters information into its database on nearly all current apprehended migrants.
Additional information in USBP apprehensions data describes:
• Arrest method. The method for the overwhelming majority of arrests is capture by USBP at the border. Other arrest methods are capture by USBP agents in the U.S. interior, capture by other law enforcement agencies, and capture at traffic checkpoints.
• Status at entry. The overwhelming majority of records have this status as “Present without Authority from Mexico,” which indicates the individual was attempting to cross the U.S.–Mexico border as opposed to entering from Canada or by sea.
• Status when found. The overwhelming majority of records indicate the individual is in transit rather than working or seeking employment.
• Time in the United States. The overwhelming majority are for arrests at entry.
• Smuggler use. Whether the individual hired a smuggler to cross the border, and if so, the price paid.
The records also describe the disposition of the individual after apprehension. Most apprehendees are returned to their countries of origin, rather than being subject to incarceration in the United States.
Apprehensions data in aggregate form (i.e., the total number of apprehensions in a given month) have been used in a large body of academic research (see Hanson  for a survey). Apprehensions tend to rise when average U.S. wages increase relative to average Mexican wages or when Mexico’s real exchange rate depreciates vis-à-vis the United States (Hanson and Spilimbergo, 1999). They tend to fall initially, but later recover, in response to increases in USBP enforcement activities (Bean et al., 1990; Cornelius and Saleyhan, 2007; Dávila et al., 2002; Donato et al., 1992; Espenshade, 1994; Kossoudji, 1992; Orrenius and Zavodny, 2003).