The distribution pattern in the 2002 census was similar to those of the 1980 and 1991 censuses, but the share of the two main groups has declined. Indo-Guyanese made up 51.9% of the total population in 1980, but by 1991 this had fallen to 48.6%, and then to 43.5% in the 2002 census. Those of African descent increased slightly from 30.8% to 32.3% during the first period (1980 and 1991) before falling to 30.2% in the 2002 census. With small growth in the overall population, the decline in the shares of the two larger groups has resulted in the relative increase of shares of the multiracial and Amerindian groups. The Amerindian population rose by 22,097 people between 1991 and 2002. This represents an increase of 47.3% or annual growth of 3.5%. Similarly, the multiracial population increased by 37,788 persons, representing a 43.0% increase or annual growth rate of 3.2% from the base period of 1991 census.. How many years did it take for the Amerindian population to rise by 22097 people?