Nineteen Sixty-four is a research blog for the Center for Applied Research in the Apostolate (CARA) at Georgetown University edited by Mark M. Gray. CARA is a non-profit research center that conducts social scientific studies about the Catholic Church. Founded in 1964, CARA has three major dimensions to its mission: to increase the Catholic Church's self understanding; to serve the applied research needs of Church decision-makers; and to advance scholarly research on religion, particularly Catholicism. Follow CARA on Twitter at: caracatholic.


Global Catholicism: Aggregating data to estimate the number of Catholics at the national level on a global scale

In a previous post, Catholic population data reported in the OCD were compared to survey-based estimates at the state-level. This is replicated here at the national-level for 70 countries where survey data are available. Survey estimates are compared to the Catholic Church’s official population reports in the Annuarium Statisticum Ecclesiae (ASE) 2005.

The surveys provide estimates of the percentage of adult respondents in two large international surveys who self-identify themselves as Catholic (see the previous post regarding the use of adult surveys to estimate total population). These surveys include the most recently released wave of the World Values Survey (WVS) for 2005 to 2008, the most recent wave of the Comparative Study of Electoral Systems (CSES) for 2002 to 2006 and the International Social Survey Programme (ISSP) for 2004 to 2006.

The survey-based estimates are then applied to total mid-year population estimates for each country in 2005 from the U.S. Census Bureau’s International Data base (IDB). In cases where there are estimates from all three surveys an average of these are used. Although imperfect, these methods are the best available for providing global comparisons.

Overall, these surveys estimate that there were 769.4 million Catholics residing in the 70 countries in 2005 for which data are available.  In these same 70 countries, the Catholic Church had estimated that there were 883.7 million Catholics (79 percent of the Church’s estimate of all Catholics globally). Thus, the Church’s estimated population for these countries is 15% higher than the aggregated survey estimate.

However, as shown in the tables above, the surveys estimate 0.0% Catholic self-identity in some of the countries where Catholics are known to reside in significant numbers (e.g., there are Catholic parishes and parishioners). These include Egypt, India, Indonesia, Iran, Kyrgyzstan, Morocco, Thailand, and Turkey. The Church reports that a total of 25.3 million Catholics reside in these countries—mostly in India (18.1 million) and Indonesia (6.5 million). Catholics are estimated to make up less than 3% of the population in both of these very large population countries. If one removes these 25.3 million from the Catholic Church’s Catholic population total to reflect the survey estimates the Church’s total Catholic population is 11.6% higher than the survey population estimate (858.4 million compared to 769.4 million).

Based on the survey estimates, the Catholic Church is over-estimating Catholic population in Europe and the Americas to a similar degree (15% in Europe and 16% in the Americas).  The Church is likely under-estimating the Catholic population of Africa and the Middle East combined (-29%). In Brazil, the largest Catholic population country in the world (regardless of the estimation method), the surveys indicate the Church is over-estimating the number of Catholics residing there by 29 million.

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