The economy of mediaeval Dundee centred on the export of raw wool, with the production of finished textiles being a reaction to recession in the 15th century. Two government Acts in the mid 18th century had a profound effect on Dundee's industrial success: the textile industry was revolutionised by the introduction of large four-storey mills, stimulated in part by the 1742 Bounty Act which provided a government-funded subsidy on Osnaburg linen produced for export. Expansion of the whaling industry was triggered by the second Bounty Act, introduced in 1750 to increase Britain's maritime and naval skill base. Dundee, and Scotland more generally, saw rapid population increase at end of the 18th and beginning of the 19th century, with the city's population increasing from 12,400 in 1751 to 30,500 in 1821.