The Index of Linguistic Diversity (ILD) is fully explained in a paper published in the online journal Language Documentation & Conservation: The paper, “The Index of Linguistic Diversity: A New Quantitative Measure of Trends in the Status of the World’s Languages”, can be downloaded from the above link.
The Index of Linguistic Diversity: A New Quantitative Measure of Trends in the Status of the World’s Languages
David Harmon and Jonathan Loh
The Index of Linguistic Diversity (ILD) is a new quantitative measure of trends in linguistic diversity. To derive the ILD we created a database of time-series data on language demographics, which we believe to be the world’s largest. So far, the database contains information from nine editions of Ethnologue and five other compendia of speaker numbers. The initial version of the ILD, which draws solely on the Ethnologue subset of these data, is based on a representative random sample of 1,500 of the world’s 7,299 languages (as listed in the 2005 edition). At the global level, the ILD measures how far, on average, the world’s languages deviate from a hypothetical situation of stability in which each language is neither increasing nor decreasing its share of the total population of the grouping. The ILD can also be used to assess trends at various subglobal groupings. Key findings:
- Globally, linguistic diversity declined 20% over the period 1970–2005.
- The diversity of the world’s indigenous languages declined 21%.
- Regionally, indigenous linguistic diversity declined over 60% in the Americas, 30% in the Pacific (including Australia), and almost 20% in Africa.