U.S. Customs and Border Protection: Trade Facilitation, Enforcement, and Security [Updated June 22, 2015] [open pdf - 1MB]
From the Introduction: "International trade is a critical component of the U.S. economy, with U.S. goods trade amounting to about $4 trillion in 2014, with merchandise imports of $2.4 trillion and exports of $1.6 trillion (see Appendix B). The efficient flow of legally traded goods in and out of the United States is thus a vital element of the country's economic security. While U.S. trade in imports depends on the smooth flow of legal cargo through U.S. ports of entry (POE), the goal of trade facilitation often competes with two additional goals: enforcement of U.S. trade laws and import security. How to strike the appropriate balance among these three goals is a fundamental question at the heart of U.S. import policies. Striking the appropriate balance among competing import policy goals is made more difficult due to the volume and complexity of trade inflows. U.S. Customs and Border Protection (CBP), the agency charged with managing the import process at the border, admitted about 30.4 million import entries per year through over 300 U.S. POEs, in fiscal year (FY) 2013. [...] This report describes and analyzes CBP's role in the U.S. import process."
CRS Report for Congress, R43014
Congressional Research Service: https://crsreports.congress.gov/