Trends in Cocaine Trafficking
"While their decline began in 2005, cocaine seizures in the United States have followed a downward trend similar to the prevalence of cocaine itself, suggesting that falling seizures reflect a decreasing supply of cocaine reaching the United States. One reason contributing to the time lag that emerges from these similar, but unsynchronized, trends, with changes in seizure data occurring earlier than changes in prevalence data, is that seizures usually occur relatively near to the start of the trafficking cycle, whereas consumption usually takes place at its end."
UNODC, World Drug Report 2012 (United Nations publication, Sales No. E.12.XI.1), p. 37.