Ireland's 19th century linen industry was one of the few successful industries in that country at the time, but the deregulation of the industry in the 1820s has made it difficult for historians to determine the amount of linen cloth exported by Ireland to England. Export receipts taken from Belfast and import receiving receipts taken from London and Liverpool can help to approximate the quantity of linen cloth exported during the 19th-century Irish famine. Much of the data concerning the Irish linen trade was taken from the Railway Commissioner's Report. The linen trade slackened in the 1830s following a fall in cotton prices; it was revived in the 1850s when the demand for cotton returned and flax-spinning mills were expanded.