ANSWER is 1971. The Decadal growth rate of population in terms of percentage was highest in INDIA in 1971.The population growth rate peaked during the decade 1971-81, perhaps in the year 1972-73 (based on the Sample REGISTRATION Scheme data).The average annual exponential growth rate declined marginally to 2.11 percent (4.5%) after having remained at a plateau for the previous two decades of 1961-71 & 1971-81. At this point, the fertility and mortality trends indicate that India will reach the replacement LEVEL fertility (Net Reproductive Rate of Unity) by the years 2010-2015. The decadal growth rate is a critical part of the census operations. It gives an overview of the percentage of total population growth in a particular decade.Some records keep track of the increase and the decrease in population. And it is called 'decadal' as the decade consists of a period of 10 years. Therefore, the decadal growth rate gives an overview of the total population growth in a particular decade. According to the provisional reports released on 31 March 2011, the Indian population increased to 1.21 billion with a decadal growth of 17.70%.The adult literacy rate increased to 74.04% with a decadal growth of 9.21%. The motto of the census was 'Our Census, Our future'.Total population: 1,210,193,422 (17.70%)Most populous state: Uttar Pradesh