CAPE TOWN - There was more representation of blacks in the middle class in South Africa last year, indicating that racial differences had narrowed -- although slightly, according to a survey published on Wednesday.

Judging by the living standards measures (LSMs), 19 percent of blacks were living in the highest category, LSM 10, last year, up from three percent in 2001, said the survey conducted by the SA Institute of Race Relations.

Divided into 10 categories, LSMs are a marketing tool developed by the SA Advertising Research Foundation with an aim to help define markets. It does not measure income but gathers data based on where people live and whether they own certain appliances and vehicles.

Compared with blacks, whites made up 65 percent of adults in LSM 10 -- the highest living standards -- in 2010, down from 87 percent in 2001.

"The data shows that the racial differences have narrowed slightly, with more representation of Africans in the top LSM groups than 10 years ago, demonstrating a growing African middle class," the institute's Lucy Holborn said.

But Holborn said this was considered an under-representation because blacks made up 76 percent of the adult population.

"There has been a shift to the higher LSMs but it is still racially skewed," she said.

Despite an increase in the number of blacks in the middle class, blacks still made up the bulk of poor in the country.

Last year, 98 percent of black people were in LSM 1, the lowest living standards, a slight decrease from 99.7 percent in 2001, the survey showed.

The biggest change took place among adults. In 2001, 11 percent of adults were in LSM 1, but by 2010, only 2 percent were in the lower LSM.

The proportion of adults in the top three LSM categories - eight to 10 - had also increased by 25 percent, according to the survey.

In 2001, 16 percent of adults were in LSMs eight to 10, while by 2010 this had increased to 20 percent, or one in five adults.