But turning dirty cash from drug sales into clean, usable currency has become harder for Mexican drug gangs as a result of tighter banking regulations at home and in the United States, their main market.
If a corrupt official or executive wants to hide the proceeds, a junket is a way to hand over cash on one side of the border and recover it on the other, in chips that can then be played and cashed out in clean foreign currency.
While the fundamentals of Modi's demonetization campaign appear sound — what government wouldn't want to curb corruption, clean out counterfeit currency, digitalized more of the economy, get a larger swath of the society into the formal market, and increase tax revenue?
The demands that the Chinese let their currency appreciate, clean up their banks or get rid of the subsidies for state-owned enterprises have been toned down.
"Corporate governance has been cleaned up, the currencies are freely floating, and the underlying economics and valuations are excellent".
For the world's poorest people, light is as much a currency as arable land and clean water, and often is just as difficult to come by.
By Adam Davidson The factory that makes the paper for U.S. currency smells like a clean barn just supplied with fresh hay.
They also accuse China of depressing its currency so exports of clean energy products will sell cheaply abroad, while foreign imports will seem artificially expensive.
The Scottish government should "come clean" about alternatives to post-independence currency union with the rest of the UK, Ed Miliband has said.
Given that the average life span of a dollar bill is only five years, billions of dollars' worth of currency are destroyed annually, replaced with clean, crisp notes.
