Prior to 2008, all data was estimated, so there may be anomalies within older data. We did our best to present the data in the most accurate light, however the data is still better viewed as presenting trends, not precise values, especially prior to 2008. Timestamps with no data are displayed as 0. For the graphs below, "K-12" refers to all K-12 organizations, including schools and districts, and "Libraries" refers to both branch libraries and library systems combined.
Averages
Prior to 2008 we collected bandwidth ranges in each state, which we used to estimate the average bandwidth values. We simply took the midpoint of each range and treated that as the average bitrate. For the highest range (10+ Mbps) we took 50 Mbps as the average value, though we acknowledge this may severely underestimate some states' actual connectivity.
Percents
To calculate the percent of organizations that are connected, we relied on a combination of estimations from previous surveys and counts from NCES school and library data.