Medium of exchange was observed as early as Oresme, Copernicus and then in 1558 by Sir Thomas Gresham, that bad money drives out good in any marketplace (Gresham's Law states "Where legal tender laws exist, bad money drives out good money"). A more precise definition is this: "A currency that is artificially overvalued by law will drive out of circulation a currency that is artificially undervalued by that law." Gresham's law is therefore a specific application of the general law of price controls. A common explanation is that people will always keep the less adultered, less clipped, sweated, less filed, less trimmed coin,
Good Girl Gone Bad Pitchfork Media described the opening lyrics of the song as inspired by "puerile psuedoporn". The album concludes with the title track "Good Girl Gone Bad", which is played with an acoustic guitar and click tracks. Released as the lead single from "Good Girl Gone Bad", "Umbrella" was sent to contemporary hit, rhythmic and urban radio in the US on April 24, 2007. The song received acclaim from music critics, who praised its production, vocals and the collaboration between Rihanna and Jay Z. "Umbrella" reached number one in more than seventeen countries worldwide, including on the UK Singles Chart and the