In the early 19th century, the economic disruption caused by the Napoleonic Wars caused United States gold coins to be worth more as bullion than as money, and they vanished from circulation. Governmental response to this shortage was hampered by the fact that officials did not clearly understand what had happened.[4] In 1830, Treasury Secretary Samuel D. Ingham proposed adjusting the ratio between gold and silver in US currency to 15.8:1, which had for some time been the ratio in Europe.[5] It was not until 1834 that Congress acted, changing the gold/silver ratio to 16.002:1. This was close enough to the market value to make it uneconomic to export either US gold or silver coins.[4] When silver prices rose relative to gold as a reaction to the California Gold Rush, silver coinage was worth more than face value, and rapidly flowed overseas for melting.