"Gospel Wattage" Formula Discussion Improving the calculations behind the "Christmas Lights" missiographic

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See the "Wattage" Around the World Table


New for 2015


What is “gospel wattage”? A new GMI concept attempting to focus mission prayer and action on the darkest parts of the tree. The estimates of “wattage” are based on a formula that includes the following factors by country: Population, number of Christians, number of evangelicals, number of charismatics, growth rate of the church from 2005-2010, and level of religious freedom/persecution. Gospel wattage by country is then combined for the regional total. To see/discuss details of how the formula works and hot it weights the various factors, scroll down.

The data sources are included in the “gospel wattage” description below. Sources have not been updated since last year’s Christmas tree graphic http://www.gmi.org/services/missiographics/library/2014/christmas-lights/ because newer data is not yet available in most of the data fields.

We got some interesting feedback about the formula last year, as you can see below; however, there was not enough of it in any particular direction for us to make changes in the formula. It is still open to correction. Feel free to offer new suggestions and/or repeat some of the suggestions from last year in order to add weight to them.

One change in the graphic this year is the “Wattage Then and Now” bar graph showing the change from 1960 to 2010. You may notice several large discrepancies between the wattage numbers for 2010 in this graph and the numbers for 2015 shown on the tree. For example, Oceania is 119W on the tree but over 200W in the graph. In such cases, trust what is on the tree as the more detailed and reliable estimate.

The data for the graph is a rougher estimate. The only way to get an "apples to apples" comparison of data from 2010 and 1960 was to use a simpler formula that omitted some of the data fields such as church growth rate and the level of persecution, which were not available for 1960. The largest discrepancies resulting from this are in the three most Christianized regions--North & Central America, South America, and Oceania--because the church growth rate slowed there and the simpler formula does not account for that.

Help us refine the formula


Rather than defend our formula, we have set up this page to explain what we did and invite discussion and refinement of the formula and/or development of similar formulas by other people. We hope that not many people will brush off the whole exercise as useless estimation. We would not have done it at all unless we believed it is generally reliable as a basis to stimulate prayer and desire to spread the light.


We admit that we made subjective decisions about how much weight to attach to each of the factors in the formula—number of Christians, persecution, church growth rate. We also admit that there may be one or more additional factors we should have included to get a truer picture of gospel wattage globally. Comments welcome.


Data sources, definitions, and categories

The basis for the data calculations are the 2010 religion and population data in Operation World (OW). We also used the OW classifications of types of Christians (“blocs” such as “Protestant”; “trans-bloc groupings” such as “evangelical”). Calculations are made by country and then added for regions.


The regions were apportioned with the Christmas tree diagram in mind, so continental groups were subdivided to get population blocs that would be correctly proportioned for the tree. UN divisions for global regions were followed wherever possible, for example, in defining “S-E Asia”. We think the pictorial representation of relative regional size is a significant piece of information that people generally do not know.


Formula calculation (explanation of details is after the list)


1. NUMBER OF CHRISTIANS. Multiply each OW Christian segment population (evangelical, Catholic, etc.) in each country by X%, where X is your guess about that segment's gospel/evangelistic “wattage” per person. (This is obviously the most subjective step in the process. See notes below this list.)

2. Add the weighted segments in each country.

3. PERSECUTION. Multiply each country total by the number (.75 to 1.5) appropriate for its rating in the Pew “Government Restrictions Index”.

4. Divide the country total population by the country total in line 3.

5. ANNUAL GROWTH RATE. Multiply the country’s annual Christian growth rate 2005-2010 (OW data) by 3, and multiply the total in line 4 by the result.

6. Add line 5 to line 4 to get the gospel watts available per person in each country.

7. Add country wattage totals for a region to get a regional wattage.


Formula calculation notes

Line 1. NUMBER OF CHRISTIANS. Weighting the relative wattage of various OW categories of Christians, (Catholic, evangelical, etc.), was undoubtedly the least precise and the most inflammatory aspect of the formula. We believe that reluctance to put a number on the relative “wattage” (spiritual light-giving) of Christians of various kinds is probably the reason that no one else, as far as we know, has created a formula that attempts to do what this one does. Perhaps they were wise not to try it. Any such “wattage value” estimate is bound to insult someone, and insults do not help the cause. So rather than publicize our numbers, which some would interpret as an insult, we invite readers to assign their own numbers.

In order to do this, the reader must assign a value to each letter as follows (some values may be the same):

Protestant – multiply by A

Independent – multiply by B

Anglican – multiply by C

Catholic – multiply by D

Orthodox – multiply by E

Marginal – multiply by F (we opted to omit this category altogether)


If the reader opts also to use Operation World’s “trans-bloc groupings” (we did use them), values must be assigned to:

Evangelical – multiply by G

Charismatic – multiply by H

Pentecostal – multiply by I


Since Pentecostals are a subset of Charismatics in the OW figures, we opted not to use the Pentecostal numbers at all in order to avoid double-counting. However, our formula does deliberately “double-count” those Charismatics who are evangelical. We did this because Charismatics have been growing so much faster than evangelicals globally over several recent decades. Their “gospel wattage” appears to be higher.


Another known limitation of our approach is that we only used one multiplier for each OW category, that is, an evangelical is assigned the same wattage multiplier no matter which country the evangelical is in. This is bound to produce some misrepresentations in particular countries where evangelicals actually have much higher or much lower wattage than our estimated global average. However, it was beyond our capacity to make country by country estimates.


Line 3. PERSECUTION.  The persecution multipliers were as follows, using four categories from the Pew “Government Restrictions Index”:

Very high – x 1.5

High – x 1.25

Moderate – x 1

Low – x .75

In other words, the formula is estimating that on average, a Christian in a low persecution country like Norway will count only ½ as much (.75 instead of 1.5) toward gospel wattage as a person in a high persecution country like Afghanistan.


Our rationale for factoring this into the formula is that the higher the persecution in a country, the higher the brightness of each person willing to be counted as a Christian there. This is both because they stand in such high visibility contrast to the society at large (widespread publicity of arrests and trials) and because the number of “Christians” for the country is not padded with fair-weather believers. On the other hand, when freedom is very high and/or Christian identity is socially desirable, many people get counted as “Christians” who are putting out no light at all.


Line 5. ANNUAL GROWTH RATE. The raw number is the estimated annual growth rate percentage for the church in a given country from 2005-2010. Believing this was a fairly strong indicator of “gospel wattage,” we multiplied this percentage by three to add weight to it in the formula. When the percentage is negative (the church is losing members), the number is deducted from the wattage. Positive percentage growth is added to the wattage.

Gospel Wattage Discussion

Posted by Larry Champoux on
Great work! I appreciate all your thinking and effort put into this. Very valuable. My one thought is that persecution can both help and hinder brightness. A Christian in a free country can publish, preach and mobilize more than in a persecuted country so that light would be brighter. But I also see your point that persecution also cleans the church of nominal folks thus making a brighter light. Maybe one solution would be to make the impact of persecution smaller on the final brightness.
Posted by jcs on
I applaud your effort. I have been on the mission field for 23 years. It looks too me like your formula overrates Catholics. I suggest that the relative weight of evagelicals, charismatics and pentecostals be increased. Not knowing what your numbers are, I can't suggest specific values. Example: I worked in San Marino briefly, saw no indication of any gospel presence at all, and was expelled from the country. SM should be much lower on the list.
Posted by Stan Nussbaum on
Thanks for the input on San Marino. We hope others will also check the figures on countries they know well, and make suggestions like you have.

We struggled with putting a number on Catholics (and all the other groups) because we had to use the same number for Catholics globally. In my experience, there is a lot of variation in the amount of gospel in Catholic churches from country to country, and the formula cannot account for this.

BTW, the first draft of the formula gave only about half as much "wattage" value to the Catholic numbers, but we decided that was too low and we raised it in the second draft. Maybe we need to change it back?
Posted by Stan Nussbaum on
Larry, re: persecution, we made a change in the formula from its first draft to the second (which was the basis for the data we published). We had used the ratio of .5, 1, 1.5, and 2 for the four levels of the Religious Restriction Index. That meant a Christian in a "very high" persecution country provided four times more wattage than one in a low persecution country.

We toned that down in the second draft to a ratio of .75, 1, 1.25, and 1.5, so there is only a factor of two not four from one end of the scale to the other. That might still be too high, as you suggest, but I think that globally there are so many nominals in low persecution countries that they more than offset this. Let's see what others have to say here.
Posted by Anil Stephen on
Thanks for this wonderful tree that you have created.
North Korea is top of the list and should be the darkest place. Unfortunately, this is not mentioned. Also Laos, Vietnam, Sri Lanka, Malaysia and Indonesia are not featured. These are dark places where persecution has been intense. Please consider adding these countries to the darkest place.


Posted by Stan Nussbaum on
In our experimental formula, intensity of persecution is only one of the factors. Other factors make North Korea 36th on our list instead of 1st, where it would be if persecution were the sole measure. The other countries you mention rank from 47th (Laos) to 74th (Indonesia) on our list. In most of them, there is a significant Christian minority, like the Chinese in Malaysia, and/or some Christian presence left over from a colonial period, like the Catholics in Vietnam. North Korea had a huge revival movement a century ago, and there is still leftover light that the forces of darkness have not been able to put out.

The countries at the top of our list either never had a significant Christian minority (Western Sahara, Yemen) or it was many centuries ago (Morocco, Tunisia, Afghanistan). Turkey, in 4th place on our list, is the most spectacular example of a country that was a Christian heartland but is now almost devoid of Christmas light.
Posted by Glen Mickel on
A "discipleship watts" tree would be beneficial as we are instructed to go and make disciples, not just converts. Would it be possible to factor in a nations "sin" index that reveals if the Christian population is actually disciples and making a difference, not just attending a church, but not following Jesus in his work among the poor and disenfranchised. Just a thought.d
Posted by Stan Nussbaum on
Glen, great suggestion, even though it will take some work to figure out how to include it next year. Regrettably (for our purposes), discipleship is virtually impossible to count. So what indicators of discipleship are countable?

One hurdle we have with anything like a "sin" index (poverty, justice, corruption, etc.) is the time lag of discipleship and observable effect on the society. For example, Europe as a whole is benefitting now from biblical ideas and values that the monks worked so hard to exemplify in the Middle Ages. But when Scandanavian countries show up as very low on the global corruption index today, it does not indicate that the countries are well discipled. It shows that they used to be, and they are still reaping the benefits though they have turned their backs on Jesus as Lord.

You are welcome to comment further, and maybe other readers will want to add ideas too. It's a very intriguing concept you are floating.
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