Why Literacy is a development indicator?

One glance at a book and you hear the voice of another person, perhaps someone dead for 1,000 years.

The Human Development Index, produced by the United Nations Development Programme (UNDP), uses education as one of its three indicators; originally, adult literacy represented two-thirds of this education index weight.

In 2010, however, the UNDP replaced the adult literacy measure with mean years of schooling. A 2011 UNDP research paper framed this change as a way to “ensure current relevance,” arguing that gains in global literacy already achieved between 1970 and 2010 meant that literacy would be “unlikely to be as informative of the future.” Other scholars, however, have since warned against overlooking the importance of literacy as an indicator and a goal for development, particularly for marginalized groups such as women and rural populations.