Connected: Rural, poor areas lag in broadband

Methodology: broadband subscribership estimates for cities and other tract subsets

Friday, March 23rd, 2012 

The Federal Communications Commission (FCC) releases data on broadband subscribership rates at the city and county level in broad ranges — like 20 percent to 40 percent — rather than exact percentages. By using a statistical method called “Monte Carlo simulation,” the Workshop was able to estimate rates for entire cities (and other groups of census tracts) by estimating the sum of all contained tracts (and calculating an uncertainty of each estimate). The accuracy of this method was verified by estimating subscribership rates for entire states and comparing these estimates to values published by the FCC.

Tract Data

The FCC doesn't release numeric subscribership estimates for geographies smaller than states. The commission does, however, provide county and census tract-specific data that assigns a category to each tract. Specifically, a "0" means there are no broadband connections, a "1" means 0-20 percent of households have broadband, a "2" means 20-40 percent of households have broadband, a "3" means 40-60 percent of households have broadband, a "4" means 60-80 percent of households have broadband, a "5" means 80-plus percent of households have broadband.

The FCC collects information from broadband providers directly via Form 477. The broadband definition used for this report was faster than 96KB/s (768 Kbps) download and 25 KB/s (200 Kbps) upload. That’s the speed identified in the economic stimulus legislation, which funded broadband projects, passed in 2009. While this rate would seem grossly inadequate for most broadband users today, it is the fastest the FCC releases at the census-tract level. The FCC definition — 200 Kbps upload or download — is even slower.

In order to obtain estimates for state and metropolitan statistical areas, we ran a “Monte Carlo simulation” that predicts the exact value of the number of housing units and the number of broadband subscribers in each tract. [For more about this general topic, see the Wikipedia article]. Demographic data for this project comes from the American Community Survey 2005-2009, which is based on a one in six sample, so the number of households is not precisely known.

Precise household unit counts are simulated on the assumption that the true number of units is normally distributed within the 90 percent margin of error given by the ACS. Tract-wise, broadband rate quantities are simulated on the assumption that actual subscribership rates are uniformly distributed within their stated range. Because there is no published range for the '5' category — it's just listed as having greater than 800 residential broadband connections per 1,000 households — we've capped our assumed distribution at 100 percent. A published distribution of tracts for the less stringent FCC standard clearly shows a substantial number of tracts with more residential broadband connections than houses, but no such chart is available for the BTOP standard.

Discussion

The FCC does not appear to provide regular state-by-state subscribership breakdowns using the BTOP/BIP standard (96KB/sec). instead, the biannual reports that accompany the form 477 data release use the laxer FCC standard (25K/second download). However, a report on the June 2009 data does include a state-by-state chart of broadband subscribership using the BTOP/BIP standard; a comparison of the Investigative Reporting Workshop estimates and the FCC's measurements follows below. We followed the convention, used in the American Community Survey, of calculating 90 percent confidence intervals.

June 2009 state-by-state comparison, BTOP/BIP standard (1000 simulations)

StateIRW estimate, 5th percentileIRW estimate, medianIRW estimate, 95th percentileFCC reported valueDifference, FCC estimate minus IRW median
Alabama 43.78 44.05 44.29 43 -1.05
Alaska 41.63 42.30 43.21 42 -0.30
Arizona 56.43 56.73 57.04 57 0.27
Arkansas 38.72 39.03 39.44 38 -1.03
California 61.14 61.20 61.27 62 0.80
Colorado 63.05 63.33 63.57 65 1.67
Connecticut 70.88 71.20 71.49 71 -0.20
Delaware 63.24 63.82 64.49 67 3.18
District of Columbia 59.66 60.24 60.96 59 -1.24
Florida 59.65 59.78 59.90 60 0.22
Georgia 54.06 54.28 54.53 54 -0.28
Hawaii 67.84 68.34 68.81 Unreported  
Idaho 48.64 49.16 49.66 48 -1.16
Illinois 57.75 57.88 58.02 57 -0.88
Indiana 49.61 49.81 50.06 50 0.19
Iowa 50.38 50.70 51.03 51 0.30
Kansas 54.18 54.49 54.87 55 0.51
Kentucky 45.74 46.02 46.27 45 -1.02
Louisiana 51.68 51.93 52.20 51 -0.93
Maine 51.98 52.39 52.81 52 -0.39
Maryland 62.78 63.02 63.25 64 0.98
Massachusetts 67.69 67.86 68.08 69 1.14
Michigan 53.10 53.22 53.35 52 -1.22
Minnesota 55.82 56.02 56.22 56 -0.02
Mississippi 36.92 37.24 37.64 36 -1.24
Missouri 46.66 46.85 47.09 47 0.15
Montana 43.55 44.12 44.64 45 0.88
Nebraska 52.68 53.01 53.49 56 2.99
Nevada 56.34 56.82 57.31 58 1.18
New Hampshire 66.11 66.56 66.96 67 0.44
New Jersey 68.46 68.63 68.77 72 3.37
New Mexico 47.82 48.18 48.68 47 -1.18
New York 62.22 62.32 62.41 65 2.68
North Carolina 53.95 54.17 54.41 53 -1.17
North Dakota 57.33 57.99 58.62 57 -0.99
Ohio 52.39 52.50 52.63 53 0.50
Oklahoma 47.18 47.45 47.74 47 -0.45
Oregon 57.74 58.05 58.39 57 -1.05
Pennsylvania 56.81 56.93 57.03 58 1.07
Rhode Island 64.79 65.26 65.72 Unreported  
South Carolina 49.04 49.36 49.68 48 -1.36
South Dakota 50.93 51.54 52.22 52 0.46
Tennessee 46.02 46.25 46.50 45 -1.25
Texas 48.86 48.98 49.08 49 0.02
Utah 57.65 57.98 58.44 58 0.02
Vermont 51.18 51.76 52.47 51 -0.76
Virginia 57.07 57.27 57.52 59 1.73
Washington 60.84 61.03 61.25 61 -0.03
West Virginia 42.70 43.01 43.48 43 -0.01
Wisconsin 53.22 53.41 53.63 54 0.59
Wyoming 53.01 53.74 54.63 53 -0.74

There's good agreement between the Workshop's estimates and official FCC figure for states in June 2009 — but it's not clear how good a predictor our simulations are in later years.

Overall, the FCC's subscribership numbers are slightly larger than the Workshop's — which makes sense given that the Workshop's estimate is based on an assumption that tracts have a subscribership rate of 100 percent or less.

It's natural to assume a greater discrepancy between the Workshop's estimates and the "real" quantities would be present when comparing Metropolitan Statistical Areas because population sizes are smaller than states. The smallest of the 100 top MSA's has a population of just over 500,000. It's worth noting, however, that the Workhop's estimates are fairly close to the FCC's numbers for the five states with populations of less than 800,000: Alaska, the District of Columbia, North Dakota, Wyoming and Vermont.

What impact does capping the data at 100 percent of households have on estimates?

To examine these effects at higher reported rates, we also estimated state-by-state subscribership rates using the less stringent HHS standard (25 KB/sec download or upload). Increasing error size with larger reported subscribership rates appears to be slightly more pronounced when examining this standard.

It's hard to know precisely how the bias in the simulated values for the less stringent standard (25KB/sec download or upload) relate to the bias in the more stringent (96KB/sec download and 25KB/sec upload) standard, but it seems apparent that the overall error in the stricter standard is lower simply because the reported values are lower. Moreover, at comparable published NTIA values it appears that BTOP-standard measurement error is slightly lower, which would make sense if there are fewer tracts 'maxed out' at 100 percent.