The Central Statistics Office, which operates under the Vatican Secretariat of State, conducts a variety of studies for the Roman Curia throughout the year. But one of the office's biggest projects is compiling the annual, 500-page Statistical Yearbook of the Church.

Of course, the yearbook tracks the Catholic population, both by a head count of the baptized in each country and as a percentage of the world's population. The latest report, based on numbers gathered Dec. 31, 2015, tallied 1.28 billion Catholics, which is about 17.7 percent of the global population.

Ten years earlier, according to the statistics office, the Catholic community numbered just over 1.1 billion, which was 17.3 percent of the population at that time.

Worldwide Catholics operate close to 118,000 hospitals, clinics, homes for the aged, orphanages, counseling centers and rehabilitation facilities. Ten years ago, the number of such facilities was less than 115,000.

When the Statistical Yearbook of the Church is released each year, one of the first figures many people look at is what the book defines as the "workforce for the church's apostolate."

For the year ending Dec. 31, 2015, that included: 5,304 bishops; 281,514 diocesan priests; 134,142 religious order priests; 45,255 permanent deacons; 54,229 religious brothers; 670,330 religious sisters; 351,797 lay missionaries; and more than 3.1 million catechists.

But the yearbook looks even deeper, for example, by giving an indication of the "pastoral workload" of priests both in relation to the number of baptized Catholics as well as to the general population.

Catholics in Tajikistan can expect personalized pastoral care. With 38 Catholics for every priest, the country has the best Catholics-to-priest ratio in the world. Of course, there are only four priests in the country and fewer than 200 Catholics. Catholics on the nine-island nation of Tuvalu in the South Pacific do nicely with a ratio of 120 Catholics for every priest.

On the other end of the scale are Qatar and Saudi Arabia, which have tens of thousands of Catholic foreign workers from countries like India and the Philippines and restrictions on the ministry of clergy. According to the Vatican, the ratio of Catholics-to-priest is 52,000-to-1 in Qatar and a staggering 125,000-to-1 in Saudi Arabia.

The worldwide average is 3,091 Catholics for every priest. The situation in North America is better than average. In Canada, there are 2,242 Catholics for every priest, and in the United States, the ratio is 1,808 Catholics for each priest.

But both Canada and the United States also made the list of more than two dozen nations where the number of priests who died in 2015 was greater than the number of new priests ordained. Most of the other countries on the list are in Western Europe.

For the Vatican, one of the most important statistics is the number of baptisms performed each year and, specifically, what percentage of those involve new Catholics who are over the age of 7, the traditional "age of reason."

In 2015, the yearbook reported, there were a total of more than 15.7 million baptisms, and just over 17 percent of them involved persons over the age of 7. The percentage of baptisms involving older children and adults was highest in Africa (32.6 percent), followed by the Caribbean (23.3 percent) and Southeast Asia (17 percent).

Further analyzing the figures on the baptism of infants and small children, the statistics office looked at the number of those baptisms for every 1,000 Catholics. For the past five years, it said, "there has been a general downward trend," which closely follows the declining birthrates in many nations.

The ratio declined over the five-year period in every region of the world. For example, in Africa in 2005, there were 13.2 baptisms for every 1,000 Catholics; in 2015, the figure was 12.3.

The ratio of Catholic marriages for every 1,000 Catholics present also declined over the five-year period.

Some other figures from the Statistical Yearbook:

– Around the world, 481 parishes are "entrusted to women religious." Both North America and Europe have 104 such parishes, while 126 parishes in South America are run by sisters.

– The two countries with the highest percentage of Catholics in the general population are: Andorra, where 99.7 percent of the population is Catholic; and Equatorial Guinea, which reported 97.2 percent of its population is Catholic. Vatican City State is not included in the survey.

– Of the 5,304 bishops in the world at the end of 2015, 886 (16.7 percent) of them were residing or ministering in a country other than the country of their birth. In 1995, there were 4,319 bishops and 15.8 percent of them were residing outside their homelands. Bishops ministering abroad include the international corps of archbishops serving as Vatican ambassadors around the world and those working at the Vatican.