Intensive militarization of the Southwest border beginning in the 1990s led to a surge in migrant deaths that continues to this day. Arizona began to see hundreds of deaths beginning in 2000–2001, as migration flows were diverted into its desert. Among the community's responses to this catastrophe, lists of the victims began to be kept, using the official reports from county medical examiner's offices. Annual deaths in Arizona's desert are in the hundreds, the cumulative total in the thousands: a minimum of 2,666 as of July 2013.
Prior to this, the U.S. Border Patrol reports (copy) that there were 29 deaths in its Tucson Sector in 1998–99 and 74 in 1999–2000.
Current-year data for the portion of Arizona covered by the Border Patrol’s Tucson Sector is compiled by the Tucson Samaritans: for October 2012 through July 2013, the figure is 161 recovered remains.
(The fourArizona border counties are Pima County, Santa Cruz County, Yuma County, and Cochise County. All but Yuma County fall within the Tucson Sector. The majority of the Arizona deaths occur in Pima County.)
When large numbers of people are dying in remote wilderness conditions, the number of bodies recovered gives an indication, but only an indication, of the true loss of life. No one knows how many are not found. Moreover, many that are found are not identified. A complete list of people who have died while crossing the border does not exist.
According to the U.S. Border Patrol (copy), using the most restrictive criteria for counting deaths, 5,570 human beings have died trying to cross the Southwest border since 1998. That is the highest precise number currently available. Many more remain unfound, uncounted, unknown.
The annual number of migrant deaths shows no signs of decline, but there is also strong evidence that crossing the border has become substantially more dangerous from year to year.
The best available measure of the risk of death is the ratio of recovered bodies to Border Patrol apprehensions in a given region and time period. In the Border Patrol's Tucson Sector (which covers the Arizona border counties, excluding Yuma County), in fiscal year 1998, there were 3 known deaths per 100,000 apprehensions.
By contrast, there were 88 known deaths per 100,000 apprehensions in fiscal year 2009—a thirty-fold increase in eleven years. See Risk of Death Higher Than Ever for Migrants and the Arizona Daily Star article cited therein.
That trend continued in fiscal year 2010, with 253 known deaths and 219,318 apprehensions (Arizona Daily Star, Dec. 18, 2010). The ratio is an unprecedented 115 known deaths per 100,000 apprehensions.