The increase in gold and silver experienced by Spain coincided with a major inflationary cycle both within Spain and Europe, known as the price revolution. Spain had amassed large quantities of gold and silver from the New World. In the 1520s large scale extraction of silver from Mexico's Guanajuato began. With the opening of the silver mines in Zacatecas and Bolivia's Potosí in 1546 large shipments of silver became the fabled source of wealth. During the 16th century, Spain held the equivalent of US$1.5 trillion (1990 terms) in gold and silver from New Spain. Being the most powerful European monarch at a time full of war and religious conflicts, the Habsburg rulers spent the wealth in wars and arts across Europe. "I learnt a proverb here", said a French traveller in 1603: "Everything is dear in Spain except silver". The spent silver, suddenly spread throughout a previously cash-starved Europe, caused widespread inflation. The inflation was worsened by a growing population with a static production level, low salaries and a rising cost of living, which damaged local industry. Increasingly, Spain became dependent on the revenues flowing in from the mercantile empire in the Americas, leading to Spain's first bankruptcy in 1557 due to rising military costs. Phillip II of Spain defaulted on debt payments in 1557, 1560, 1575 and 1596. The increase in prices as a result of currency circulation fuelled the growth of the commercial middle class in Europe, the "bourgeoisie", which came to influence the politics and culture of many countries.