placestats

Religious adherents and Clear days

A county is not a congregation. Counties where more people are counted as adherents (members of a religious group) also tend to differ on the other measure, and that is all. It does not follow that the adherents are the people with the different score. Making that leap is called the ecological fallacy: reading a pattern across places as a fact about individual people. It is as easy to fall into here as with the voting pairs. Two things about the counting matter too. Adherents are counted where their congregation meets, not where they live, so thirty very small counties exceed 100%. And a denomination that did not report is missing, not zero. That undercounts membership most where churches are least formally organised.

Where Religious adherents is higher, Clear days tends to be higher. The link is weak: +0.31 across 3,121 counties, on a scale from −1 (opposite) to +1 (in step). That figure compares places with the same population density, income and education, so those differences can't explain it. It holds inside states too. Measured separately within each of 40 states, the middle value of the link is +0.06.

Holds after adjusting

Every place, plotted

One dot for each place reporting both measures. Hover over or tap a dot to see its name and values. The thin line is the straight line that best fits the dots. The bold line, shown for counties, is the link after adjusting for density, income and education. A dot far from the lines is a place that does not follow the pattern.

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What each measure is

Religious adherents

Members, their children, and others who attend regularly, as a share of the population. It is above 100% in thirty very small counties, where a congregation draws people from beyond the county it sits in.

US Religion Census (ASARB) · Religion Census 2020 files; 2010 from the ARDA, RCMSCY10 and RCMSST10

Clear days

The number of days in the year when clouds blocked less than 7% of the sunlight, so the ground got at least 93% of what a cloudless sky would give. It is the closest measure here to a count of sunny days. It is a NASA estimate from weather satellites for squares of land about 60 miles across, not a count by someone watching the sky, and nearby counties often share a value. The 93% line was chosen so that, on average, the count matches NOAA's counts of clear days at 64 weather stations. There, a clear day is one with three tenths of the sky or less covered by cloud in daylight. It starts in 2001, since the older satellites count clear days differently.

NASA POWER (Prediction Of Worldwide Energy Resources) · NASA POWER daily regional API, community RE, ALLSKY_SFC_SW_DWN / CLRSKY_SFC_SW_DWN

Highest and lowest

Where each measure is highest and lowest among the places reporting both (2023), with the other measure beside it. This is shown for every size of place where both are published. Metro-area values are added up from their counties. A measure that cannot be added up across counties, such as a middle value (median), has no metro figure. Counts are shown per 1,000 residents, since raw totals would only list the largest places. Cities and towns and ZIP codes are shown where the Census survey or the CDC publishes them; most other sources stop at the county. They are shown for places of 5,000 residents or more, and only where the survey’s margin of error is small enough for the figure to be usable. The CDC publishes its health estimates for cities in a version adjusted for age, so places with older or younger people can be compared fairly, but not for ZIP codes.

Counties

By religious adherents

By clear days

States

By religious adherents

Religious adherentsClear days
Highest
Utah76.1112
Alabama63.6121
Louisiana63.3119
Oklahoma61.2158
Mississippi59.4128
Lowest
New Hampshire27.284
Maine30.881
Oregon33.1103
Montana34.982
Alaska35.117

By clear days

Religious adherentsClear days
Highest
Arizona44241
Nevada41.6186
New Mexico52.5168
California44.8168
Oklahoma61.2158
Lowest
Alaska35.117
Vermont37.662
Michigan39.779
Hawaii41.580
Maine30.881
Metro areas

By religious adherents

Religious adherentsClear days
Highest
Camden, AR105131
Mount Pleasant, TX98.4135
Brigham City, UT-ID8996
Provo-Orem-Lehi, UT88.7103
Nogales, AZ88.2210
Lowest
Crescent City, CA14.199
Eureka-Arcata, CA19.285
Athens, OH19.293
Port Townsend, WA20.782
Pahrump, NV21.6227

By clear days

Religious adherentsClear days
Highest
Yuma, AZ35.1273
El Centro, CA86.3258
Phoenix-Mesa-Chandler, AZ46.6252
Payson, AZ33.1236
Lake Havasu City-Kingman, AZ25.6234
Lowest
Juneau, AK32.63
Anchorage, AK35.711
Hilo-Kailua, HI41.814
Fairbanks-College, AK30.229
Ketchikan, AK31.433

Counties furthest from the pattern

Compared with the straight line that best fits all 3,144 counties: the five with far more clear days than their religious adherents would suggest, and the five with far less.

Religious adherentsClear days
Above the line
La Paz County, AZ30.6272
Yuma County, AZ35.1273
Maricopa County, AZ47.2254
Mohave County, AZ25.6234
Gila County, AZ33.1236
Below the line
King County, TX452194
Yakutat City and Borough, AK61.33
Aleutians East Borough, AK41.76
Juneau City and Borough, AK32.63
Kodiak Island Borough, AK338

Two series, one county

Both measures over time for a county you pick. The two charts are stacked, so they share only the years along the bottom. You can pick from the thirty largest counties reporting both. This panel covers 2010–2024, and a measure published only once shows as a single dot.

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Every version of the link

Each row measures the same link, from −1 to +1, in a different way. If the rows mostly agree, the link does not depend on one choice of method.

Before adjusting for anything+0.3283,121 counties reporting both
After adjusting for density, income and education+0.314the part of the link that is not just how urban, rich and educated a place is
Also adjusting for population size+0.323size taken out as well as density
Also comparing only within each state+0.129each county is compared only with others in its own state, so this is no longer a comparison between states
Also holding winter sunshine equal—compares counties that get the same sunlight in winter as well. If this is much weaker, part of the link is a difference between sunny and grey regions (more)
Giving bigger counties more weight+0.112the adjusted link for the average resident rather than the average county. With this weighting, the data counts for about 287 equally weighted counties
Middle value inside single states+0.055the link worked out inside each of 40 states with at least 20 counties reporting
Using ranks, after adjusting+0.344uses each county’s rank, not its value, so a few extreme counties cannot create the link

How much to believe it

Could it be chance?

The p-value is the chance of seeing a link this strong if there were really none. A value of 0.05 or less means the link is unlikely to be chance. Very small values are written in short form: 3.1e-16 means 0.00000000000000031, and the bigger the number after “e-”, the smaller the value. Treating every county as a separate case gives p = 1.7e-72. But counties in the same state tend to resemble each other, so the better figure allows for that: p = 8.0e-5. The site tested 32,131 pairs, and testing so many turns up some flukes. The q-value allows for that too. For this pair it is 1.4e-71.

Do nearby places look alike?

Moran’s I measures how much nearby places look alike: 0 means no map pattern, and higher means neighbours are more similar. For the part of each county that the adjustment leaves unexplained, it is +0.82 (p = 0.001). That unexplained part still clusters on the map. So some regional factor shared by both measures is not accounted for.

Did they change together?

Not measurable: at least one of these is published for too few of the years a change needs (2014–2019 or 2019–2023), or for too few counties in both.

Related pairs

Association only. Nothing here shows that either measure changes the other. This describes counties, not the people in them. Two measures going together across places does not mean the same people have both. How the US county data works · Explore Religious adherents and Clear days