There was a significant population increase during the 18th and 19th centuries, which the writer Esaias Tegnér in 1833 attributed to "the peace, the smallpox vaccine, and the potatoes". Between 1750 and 1850, the population in Sweden doubled. According to some scholars, mass emigration to America became the only way to prevent famine and rebellion; over 1% of the population emigrated annually during the 1880s. Nevertheless, Sweden remained poor, retaining a nearly entirely agricultural economy even as Denmark and Western European countries began to industrialise.