Lessons from the 75-year-old National Sample Survey

Its impressive history tells us much about innovation, autonomy and state-level data collection

- PRAMIT BHATTACHARYA

At an event to commemorate 50 years of the National Sample Survey (NSS) in 2001, the then prime minister Atal Bihari Vajpayee noted that these surveys had contributed "invaluable raw material" to India's development plans, even though their contribution was often "unseen and unhonoured." "It is not often recognized that behind every piece of statistical information lies the dedicated work of hundreds of NSS investigators who have conducted painstaking surveys and interviews, often in remote areas," he said.

The 1999-2000 NSS consumption expenditure survey suggested that poverty had declined sharply compared to the mid-90s, Vajpayee pointed out. Had any politician made this claim, it would have been questioned, he said. But nobody could question the authenticity of the NSS survey, he added. "Governments come and go, but an autonomous organization like yours functions without being affected by political and governmental changes," said Vajpayee.

While Vajpayee was right about the value of NSS data, he picked the wrong example to highlight his point. The 1999-2000 consumption data turned out to be extremely contentious. NSS had faced criticism in the 1990s for failing to capture the country's changing consumption trends. In response, the NSS team ran a series of trials to modify its questionnaires. Even before the experiments could reach their logical end, the 1999-2000 round questionnaires were revised. The hurried revisions led to a flawed survey. Eventually, that round was deemed incomparable with other NSS rounds and later excluded from the Planning Commission's official poverty estimates.