Ranking the World’s Most Populous Cities, Over 500 Years of History

Visualizing the World’s Most Popular Religions

According to some estimates, there are over 4,000 religions, faiths groups, and denominations that exist around the world today. Researchers and academics generally categorize the world’s religions into five major groups: Christianity, Islam, Buddhism, Hinduism, and Judaism.

This graphic by Chit Chart visualizes the most popular religions around the world, using the latest available data from Index Mundi’s world demographics.

In addition to the five major religious groups, the graphic includes two more categories: one for a collective of Folk religions and another for people who are unaffiliated with a religion.

The Religions with the Most Followers

Although the number of people who follow a religion has decreased in recent decades, 82.8% of the global population still identifies with one of the world’s major religions.

Here’s a breakdown of the most popular religions, ranked by their following as a percentage of the world’s population:

Christianity has the largest following with approximately 31% of the global population. Muslims make up the second-largest religious group, accounting for 23.2% of the world’s population.

Roughly 16.4% of the global population is unaffiliated with a religion. This figure exceeds the percentage of people who identify with Hinduism (15%), Buddhism (7.1%), Folk Religions (5.9%), or Judaism (0.2%).

The World’s Religions from Oldest to Newest

Hinduism is considered the oldest religion in the world, originating in the Indus River Valley (modern-day Pakistan) circa 7000 BCE.

While Judaism came after Hinduism, it is thought to be the oldest of the three monotheistic Abrahamic faiths, making it older than Christianity and Islam.

It began circa 2000 BCE in the Southern Levant (modern-day Israel, Palestine, and Jordan). By contrast, Christianity was founded in the 1st century and began as a movement within Judaism.

Scholars typically date the creation of Islam to the 7th century, making it the youngest of the world’s major religions on this list. Islam was established in Mecca (modern-day Saudi-Arabia).

One religion that’s not included on this list is Sikhism. Founded in the late 15th century, it’s relatively new, especially compared to other religions like Hinduism or Judaism. Yet, despite being new, Sikhism has a large following—according to some estimates, there are over 25 million Sikhs worldwide.

What are Folk Religions?

A folk religion is defined as an ethnic or cultural practice that exists outside the theological doctrine of organized religions.

Lacking sacred texts, Folk religions are more concerned with spirituality than rituals or rites. Examples of Folk religions include Native American traditions, Chinese folk religions, and traditional African religions.

Since Folk religions are less institutionalized, they are especially challenging to measure and often excluded from surveys. With that said, an estimated 5.9% of the global population (approximately 430 million people) practice a Folk religion.

The Fastest-Growing Religions

While Islam is the newest of the big five religions, it’s currently the world’s fastest-growing one too. For context, here’s the estimated percent change among the seven religion categories, between 2015 and 2060:

Islam’s rapid growth means it may surpass Christianity as the world’s largest religion within the next half-century. What’s causing this growth?

According to Pew Research Center, the main reason is simply demographics—on average, Muslim women have 2.9 children, which the average of all non-Muslims is 2.2.

Muslims are also concentrated in Africa and the Middle East, the two regions predicted to have the highest population increases in the next few decades.

A Decade of Population Growth and Decline in U.S. Counties

There are a number of factors that determine how much a region’s population changes.

If an area sees a high number of migrants, along with a strong birth rate and low death rate, then its population is bound to increase over time. On the flip side, if more people are leaving the area than coming in, and the region’s birth rate is low, then its population will likely decline.

Which areas in the United States are seeing the most growth, and which places are seeing their populations dwindle?

This map, using data from the U.S. Census Bureau, shows a decade of population movement across U.S. counties, painting a detailed picture of U.S. population growth between 2010 and 2020.

Counties With The Biggest Population Growth from 2010-2020

To calculate population estimates for each county, the U.S. Census Bureau does the following calculations:

 
From 2010 to 2020, Maricopa County in Arizona saw the highest increase in its population estimate. Over a decade, the county gained 753,898 residents. Below are the counties that saw the biggest increases in population:

Phoenix and surrounding areas grew faster than any other major city in the country. The region’s sunny climate and amenities are popular with retirees, but another draw is housing affordability. Families from more expensive markets—California in particular—are moving to the city in droves. This is a trend that spilled over into the pandemic era as more people moved into remote and hybrid work situations.

Texas counties saw a lot of growth as well, with five of the top 10 gainers located in the state of Texas. A big draw for Texas is its relatively affordable housing market. In 2021, average home prices in the state stood at $172,500—$53,310 below the national average.

Counties With The Biggest Population Drops from 2010-2020

On the opposite end of the spectrum, here’s a look at the top 10 counties that saw the biggest declines in their populations over the decade:

The largest drops happened in counties along the Great Lakes, including Cook County (which includes the city of Chicago) and Wayne County (which includes the city of Detroit).

For many of these counties, particularly those in America’s “Rust Belt”, population drops over this period were a continuation of decades-long trends. Wayne County is an extreme example of this trend. From 1970 to 2020, the area lost one-third of its population.

U.S. Population Growth in Percentage Terms (2010-2020)

While the map above is great at showing where the greatest number of Americans migrated, it downplays big changes in counties with smaller populations.

For example, McKenzie County in North Dakota, with a 2020 population of just 15,242, was the fastest-growing U.S. county over the past decade. The county’s 138% increase was driven primarily by the Bakken oil boom in the area. High-growth counties in Texas also grew as new sources of energy were extracted in rural areas.

The nation’s counties are evenly divided between population increase and decline, and clear patterns emerge.

Pandemic Population Changes

More recent population changes reflect longer-term trends. During the COVID-19 pandemic, many of the counties that saw the strongest population increases were located in high-growth states like Florida and Texas.

Below are the 20 counties that grew the most from 2020 to 2021.

Many of these counties are located next to large cities, reflecting a shift to the suburbs and larger living spaces. However, as COVID-19 restrictions ease, and the pandemic housing boom tapers off due to rising interest rates, it remains to be seen whether the suburban shift will continue, or if people begin to migrate back to city centers.