From Imperial Twilight: The Opium War and the End of China’s Last Golden Age, by Stephen R. Platt (Knopf, 2018), Kindle pp. 304-307:
There was nothing the government could do about the weather, but the root cause of the economic turmoil in the 1830s, and the problem from which many of the others grew, was a human one: China’s monetary system had gone haywire. It was mainly a problem of currency, of which the Qing dynasty had two primary forms: copper for small transactions and silver for large ones. Copper came in minted coins (with holes through the middle so they could be strung on a loop for convenience), while domestic silver—nearly pure and known in English as “sycee”—was unminted, traded by weight in units of measurement called taels that were just under an ounce. In normal times, a tael of silver was worth a thousand copper coins, and, value for value, the excessive difficulty of moving large amounts of copper between provinces meant that silver was the medium through which all long-distance trade was conducted within the empire. Silver was also, significantly, the basis on which tax quotas were assessed. By contrast, copper was the medium of the rural marketplace and menial wages. Nearly all of the income and savings of the lower classes of China—farmers, hired laborers, craftspeople—were in copper coins.
The crisis was that the value of silver had begun to rise sharply, and as it rose the exchange rate between silver and copper skewed out of control. From the ideal rate of 1,000 copper coins per tael of silver in the eighteenth century (even less at times, which was a boon for peasants since it meant their copper money was worth more), it had risen to 1,200 by the time Daoguang came to the throne. By 1830 it reached 1,365 copper coins per tael of silver and showed no signs of stopping. Since taxes were assessed in a fixed amount of silver, which had to be purchased with copper currency, this meant that by the early 1830s the peasants of China had suffered a nearly 40 percent increase in their effective tax burdens for reasons none fully understood. And as with nearly every problem in the empire, the corruption of officials made a bad situation even worse, as tax collectors commonly charged even higher rates of exchange so they could pocket the proceeds. By the late 1830s, some regions were reporting copper–silver exchange rates as high as 1,600 to 1, with tax collectors independently demanding as much as 2,000 copper coins per tael of silver owed. This dramatic decline in the worth of copper currency was disastrous for the general population, piling economic hardship on the poor who could scarcely bear it and sparking widespread tax protests that layered on top of all the other sources of dissent against the government. But although the emperor could occasionally grant tax amnesties to regions afflicted by floods or drought, the government quite desperately needed every tael of revenue it could get and so the exactions continued.
Even with that outflow of sycee silver, however, the inflow of Spanish dollars to purchase tea and silk at Canton should have been able to maintain a relatively steady overall silver supply in China (and in fact, since the late eighteenth century Spanish dollars had been preferred even over native sycee in some of China’s most important domestic markets). But on that count, a range of forces far beyond China’s borders came into play. First, it had been American merchants who brought most of the silver to China in the early nineteenth century (fully one-third of Mexico’s entire silver output between 1805 and 1834 was carried to China by Americans). But a shift in U.S. government monetary policy in 1834 made silver more expensive for American merchants, so they switched abruptly to using bills of exchange—which were acceptable to the Hong merchants but resulted in a decline in the amount of tangible silver entering the country from abroad. With the drop in American imports, China, which for centuries had been the world’s largest net importer of silver, unexpectedly turned into an exporter of the metal.
In the even bigger picture, though, what the Chinese scholars who blamed foreign trade and opium for the scarcity of silver in China did not realize was that it wasn’t just a Chinese problem: by the 1820s, silver was becoming scarce everywhere. Most of the world’s supply at this time had come from mines in Spanish Mexico and Peru (thus the importance of the Spanish dollar), but national revolutions in Latin America that began in the 1810s shut down those mines and choked off the world’s largest fonts of the precious metal. Global production of silver declined by nearly half during the 1810s—the same time its value began to creep upward in China—and it continued to decline during the decade that followed. The ramping up of the opium trade in 1820s China thus coincided fatefully with the onset of a global slump in silver output that would last for the next thirty years.
Regardless of where the specific blame lay, it was a devastating confluence of economic forces for China: the loss of sycee through the opium smuggling trade, the global scarcity of silver after the Latin American revolutions, and the drying up of American silver imports into China together helped cause a catastrophic decline in the empire’s supply of the metal. And it was a vicious cycle, for as silver became more valuable in China, wealthy families and businessmen would hoard it, removing even more from circulation and making the problem worse.