The economy of Kerala is the 10th-largest in India with in gross state domestic product (GSDP) and a per capita GSDP of . Kerala has the lowest positive population growth rate in India, 3.44%; the highest Human Development Index (HDI), 0.784 in 2018 (0.712 in 2015); the highest literacy rate, 96.2% in the 2018 literacy survey conducted by the National Statistical Office, India; the highest life expectancy, 77 years; and the highest sex ratio, 1,084 women per 1,000 men. Kerala is the second-least impoverished state in India according to the Annual Report of Reserve Bank of India published in 2013. The state topped in the country to achieve the Sustainable Development Goals according to the annual report of NITI Aayog published in 2019. The state has witnessed significant emigration, especially to the Arab states of the Persian Gulf during the Gulf Boom of the 1970s and early 1980s, and its economy depends significantly on remittances from a large Malayali expatriate community. Hinduism is practised by more than half of the population, followed by Islam and Christianity. The culture is a synthesis of Aryan, Dravidian, Arab, and European cultures, developed over millennia, under influences from other parts of India and abroad.