(CNN) -- The number of arrests made by U.S. Border Patrol agents decreased dramatically in the last three years, according to new statistics released Monday by U.S. Customs and Border Protection.
During fiscal year 2011, which ended September 30, agents made 340,252 arrests. That number represents a 53% decrease from fiscal 2008's 705,005 arrests, and is only one-fifth the number of arrests when they were at their peak with 1.6 million in fiscal year 2000.
The number of yearly arrests made by U.S. Border Patrol agents is seen as a key indicator of illegal immigration in the United States.
Reacting to the latest numbers, CBP Commissioner Alan D. Bersin said that "these numbers illustrate the investments made by CBP to improve border security, increase efficiencies and facilitate the flow of legal travel and trade through our nation's borders and land ports of entry."
But Ira Mehlman, spokesman for the Federation for American Immigration Reform (FAIR), said the numbers "obviously (do not) tell us how many people managed to enter the United States illegally. We do not know what factors have led to the drop in apprehension numbers."
Mehlman, whose group advocates changing policies to decrease the number of immigrants coming to the United States, added that "the drop in apprehensions since 2008 can be attributed in part to the recession. Illegal aliens are primarily attracted by the prospect of jobs in the U.S. As we all know, there have been far fewer jobs available in recent years."
According to CBP officials, out of the 340,252 arrested during fiscal year 2011, about a quarter -- 87,334 people -- had a record in the FBI's Integrated Automated Fingerprint Identification System. This federal database contains the names of individuals with criminal charges and convictions.
Another significant figure is the number of people arrested with serious convictions. At ports of entry, CBP officers arrested 8,195 people wanted for crimes including murder, rape, assault, and robbery.
Arizona was the state with the largest number of border apprehensions at 129,118 followed by Texas (118,911), California (72,638), and New Mexico (6,910).
CBP officials also reported that in fiscal year 2011 officers seized nearly 5 million pounds of narcotics, which represents a 20% increase from the previous year and $126 million in undeclared currency.