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Purdue Center for
Regional Development

Digital Divide Index (DDI)

The digital divide is the number one threat to community economic development in the 21st century. Public policy 101 argues that a problem needs to be defined before exploring potential solutions.

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The Digital Divide Index or DDI ranges in value from 0 to 100, where 100 indicates the highest digital divide. It is composed of two scores, also ranging from 0 to 100: the infrastructure/adoption (INFA) score and the socioeconomic (SE) score.

The INFA score groups four variables related to broadband infrastructure and adoption: (1) percent 2010 population without access to fixed broadband of at least 25 Mbps download and 3 Mbps upload; (2) number of residential broadband connections with at least 10 Mbps download and 1 Mbps upload; (3) average maximum advertised download speeds; and (4) average maximum advertised upload speeds.

The SE score groups three variables known to impact technology adoption: (1) percent population ages 65 and over; (2) percent population 25 and over with less than high school; and (3) individual poverty rate. In other words, these variables indirectly measure adoption since they are potential predictors of lagging technology adoption.

These two scores are combined to calculate the overall DDI score. If a particular county or census tract has a higher INFA score versus a SE score, efforts should be made to improve broadband infrastructure. If on the other hand, a particular geography has a higher SE score versus an INFA score, efforts should be made to increase digital literacy and exposure to the technology’s benefits.

The DDI measures primarily physical access/adoption and socioeconomic characteristics that may limit motivation, skills, and usage. Due to data limitations it was designed as a descriptive and pragmatic tool and is not intended to be comprehensive. Rather, it should help initiate important discussions among community leaders and residents.

Below is the DDI map showcasing county-level data. Darker blue denotes a lower digital divide as measured by the DDI while a darker red denotes a higher digital divide. Click on any county to obtain more information.


Below is the DDI map showcasing Census tract-level data. Darker blue denotes a lower digital divide as measured by the DDI while a darker red denotes a higher digital divide. Click on any tract to obtain more information.