However, the large volumes of precious metals from America led to inflation, which had a negative effect on the poorer part of the population, as goods became overpriced. This also hampered exports, as expensive goods could not compete in international markets. The port of Sevilla in the 1500s. As required by law, all trade with the colonies in the Americas went through this port. Domestic production was heavily taxed, driving up prices for Aragon and Castile-made goods, but especially in Castile where the tax burden was greater. The sale of titles to entrepreneurs who bought their way up the social ladder (a practice commonly found all over Europe), removing themselves from the productive sector of the economy, provided additional funds. The overall effect of plague and emigration reduced Spain's population from over 8 million in the last years of the 16th century to under 7 million by the mid-17th century, with Castile the most severely affected region (90% of the Kingdom population were in Castile, as an example, in 1500, Castile 6 million, Aragon 300.000 hab. ]