A tribal-built broadband network on Washington State’s Colville Reservation was associated with an income increase of about 4% in communities as they gained connectivity, according to new research examining a rollout that began in 2013.

The study focuses on the economic effect of introducing usable broadband where commercial carriers had declined to build. Before the deployment, public facilities on the reservation relied on T1 connections delivering about 1.5 Mbps. The Confederated Tribes of the Colville Reservation subsequently built a hybrid network combining fiber with fixed wireless links from mountaintop sites, increasing connectivity at community centers and government offices to symmetric 100 Mbps.

The network was financed with tribal funds and nearly $2.8 million in federal grants, according to an account of the research published by Internet Society Pulse. Nespelem and Omak were connected in 2013, followed by Inchelium and Keller in 2014. Researchers Thomas Stratmann and Pradyot Sharma of George Mason University used that staggered deployment to compare economic outcomes between communities connected earlier and those connected later.

Income rose about 4% as communities came online. Paid employment at local establishments also increased, although the researchers describe that estimate as too imprecise to establish the magnitude of the effect. The income gains were concentrated among existing tax filers rather than resulting from an increase in the number of filers.

A separate comparison with similar reservations produced a much larger increase—about one-third in per-capita income among American Indian residents—but the researchers caution against attributing that difference to broadband. Other developments included a new tribal casino, wildfires, a federal trust settlement and a reorganization of tribal businesses. They therefore treat the within-reservation estimate of roughly 4% as the more credible measure of the network’s effect.

The measured gains did not coincide with a substantial increase in household broadband subscriptions. Instead, employment growth was concentrated in education and tribal administration, consistent with a deployment that initially connected government offices, schools and health services. The researchers say the evidence is consistent with broadband reducing institutional coordination costs, while cautioning that the study covers a single reservation and uses ZIP-code-level data.

The findings also bear on continuing investment in tribal connectivity. The Colville Tribes have since received a separate $48.4 million federal award for a broadband expansion intended to connect 2,867 unserved Native American households through fiber and wireless infrastructure.