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The Eastern Cape population appears not to have grown at the same rate as other regions over the past 15 years.
Figures released by Statistics South African on Tuesday show that Eastern Cape population was 6.1m in 1996, 6.3m in 2001 and 6.6m following last year's census.
The population of neighbouring Western Cape has grown far more rapidly, from 4m in 1996, to 4.5m in 2001 and up to 5.8 m in 2011.
The country's smallest province, Gauteng, with 12.3m people, has overtaken Kwazulu Natal, with 10.3m people, as the country's most populous province.
The country's largest province, the Northern Cape has, by contrast the least number of people at 1.1m.
Official census statistics released show that there are 51.8m people living in South Africa in October last year, about 7m more than the last big count in 2001.
Meanwhile, president Jacob Zuma, says although great strides have been made to
improve the lives of the people, much more can be done.
Zuma said there was really great improvement on the educational front, but some aspects still worry him.
He says its heartening to note that the proportion of people who completed higher education has increased from 7.1% in 1996 to 12.3% in 2011.
"These figures tell us that at the bottom of the rank is the black majority who continue to be confronted by deep poverty, unemployment and inequality despite the progress we have made since 1994" Zuma said.
Meanwhile, the president says the use of the bucket toilet system has been halved from 3.9% in 2001 to 1.9% in 2011.
"Eight in ten households in Gauteng and Western Cape have access to flushing toilets, on the contrary much effort still needs to go into providing toilet facilities to some communities in the EC, Limpopo, Mpumalanga and Kzn"
