Nagaland is India’s most diverse state linguistically, while Kerala is the least diverse, according to a report by Mint.

The report applies the Herfindahl-Hirschmann Index (HHI) formula to the 2011 linguistic census data.

The census document classifies languages into two levels — namely “language” and “mother tongue.”

The report classifies the former as “language” and the latter as “dialect”, comparing each Indian state on these parameters.

The report uses the HHI — originally developed to quantify competition or monopoly in an industry. HHI is defined as the sum of the square of the market share of each company in an industry.

According to the 2011 census, Nagaland has 14 languages and 17 dialects, with Konyak being the largest language having a 46 percent share.

In Kerala, over 97 percent of the population identifies Malayalam as their mother tongue.

The report states that in Himachal Pradesh, 86 percent of the people identify Hindi as their mother tongue.

Hindi spoken in the state is further divided into dialects, taking the total number of effective languages to nearly 6. The report cites the example of Pahari, a dialect of Hindi which is spoken by 32 percent of the state’s population.

Similarly in Bihar, where 78 percent of the population speaks Hindi, the state's effective languages are 1.6. However, when broken down into dialects, only 26 percent of the population speaks Hindi, the report adds.

In the states of Rajasthan and Chhattisgarh, the dialects Rajasthani and Chhattisgarhi dominate respectively when measured at dialect level.