DAR ES SALAAM (Reuters) - Tanzania will issue data on its rebased gross domestic product (GDP) in mid-November, with analysts estimating the size of the $33.26 billion economy could increase by about 20 percent. The rebasing process allows statisticians to update their estimates to take account of technological innovations, giving investors a clearer view of the amount and types of activity in the economy. The state-run National Bureau of Statistics (NBS) said it would release the new data in mid-November and not on Friday as it had previously said. It gave no reason for the postponement. The agency said Tanzania, where farming is the country's economic mainstay, had updated the base year it uses to calculate economic output to 2007 from 2001. Tourism, mining, communications and financial services are the other key sectors. Tanzania has made big natural gas discoveries, with revenues expected to give a boost to the economy by 2020. The statistics office said the revised GDP for 2007 was 26.77 trillion shillings ($15.73 billion), a 27.8 percent increase from the 2001 economic output. "I predict that the size of Tanzania's economy will likely increase by between 20 and 30 percent after the GDP rebasing," Humphrey Moshi, professor of economics at the University of Dar es Salaam, told Reuters. "A bigger economy will attract more investors. But there is a need to make sure that the economy lowers inequalities, creates employment and reduces poverty - otherwise it just becomes a game of numbers." Tanzania's economy grew 7 percent in 2013, up from 6.9 percent a year ago and the government expects it to expand 7.2 percent this year. Nigeria this year overtook South Africa to become the continent's largest economy when it updated its base year to 2010 from 1990. Kenya, East Africa's biggest economy, saw its GDP revised up by 25 percent to $53.4 billion in 2013 after rebasing, from $42.6 billion previously. (1 US dollar = 1,702.0000 Tanzanian shilling)