The state income (GSDP Current prices at factor cost) of Kerala,India is comprises four series with bases 2004-05,1999-2000,1993-94,1980-81 and 1970-71 (see http://www.ecostat.kerala.gov.in/index.php/state-income-reports/115.html) I need a long run series of state income from 1970-71 to 2014-15.My question is what is the best method to splice the data and how?.