In the United States, the fertility rate has reached a record low of 1.76. The fertility rate in the United States fell to an all-time low last year. Americans' average life expectancy, meanwhile, sits at a relatively high 78.7 years.
Many experts say the 2008 economic recession and high college tuition are contributing to this trend.
According to a 2018 survey in The New York Times, however, adults who want kids say they sometimes end up having few, or zero, kids due to the high cost of childcare. The average cost of full-time childcare exceeds $10,000 a year in several states, according to Child Care Aware of America.
The US birth rate has remained below "replacement level" since the 1970s, which means not enough children are being born to keep the population at a steady level.
Last year, the US Census Bureau wrote in a paper that women who have kids between the ages of 25 and 35 have more difficulty in getting fair pay than women who give birth outside of that range. American women are now having children older than ever.
Spain has more deaths than births each year, and some towns are already nearly abandoned.
Spanish women tend to give birth later in life than most other European women, and Spaniards also live longer than anyone else in the European Union. On average, women in Spain have 1.5 children.
In Spain's northeastern Aragon region, one village already shows what a demographic time bomb can look like. The only remaining residents of La Estrella are two people in their 80s.
Last year, the Spanish government hired a special commissioner to determine how to reverse falling birth rates.
A rise in immigration to Italy has not helped the country steer clear of becoming a demographic time bomb.
A record-low 464,000 children were born in Italy last year, and the country's mean age has surpassed 45 for the first time ever.
Many Italians want to have two or more children, The Local reported, but cite difficulties in finding employment as a factor in their decisions not to.
The population of Bulgaria, the European Union's poorest member, may soon become as low as it was in the aftermath of World War II, Bloomberg reported.
Bulgaria's population is shrinking faster than any other country in the world; it is expected to hit only 5.4 million in 2050, down from 7 million last year, according to Quartz.
In addition, the country has seen an increase in emigration as citizens seek job opportunities elsewhere. Bulgaria's fertility rate is only 1.46 children per woman.
Since Latvia joined the European Union in 2004, nearly 20 percent of the country's population has left to seek employment in other parts of the bloc, such as Germany and the United Kingdom.
Latvia's population, reported to be nearly 2 million last year, is estimated to fall to 1.52 million by 2050, according to Quartz.
The South Korean government has offered cash incentives to people who have more than one child, as the fertility rate currently sits at 1.26 children per woman – too low to maintain a stable population.
Amid the declining fertility rates, some South Koreans have said they are not having children due to a lack of financial stability, according to Quartz.
Demographers say South Korea's low fertility rate is linked to women having children at an increasingly later age. In 2017, the average age of a Korean woman having a first child surpassed 31. It was the oldest average in the world.
Unlike other countries with similarly low fertility rates, Japan has not seen a significant influx of immigrants. A low number of workers in the country decreases the amount of tax money going toward retirement and healthcare services for older residents, who are growing in numbers.
The United Kingdom's birth rate has fallen to its lowest level in a dozen years, The Times reported. At the same time, the number of British residents age 65 or older is rising due to better healthcare and higher living standards.
The UK's referendum to leave the European Union has led to a decrease in the number of immigrants, who are generally younger, leading to an increasingly older population.
According to The Guardian, the number of elderly people without social care has peaked, with one in seven lacking adequate support. About 1.4 million residents who are older than 65 are not receiving help with getting up or getting washed.
Singapore's fertility rate, 0.83, is the lowest in the world.
A 2017 report by the Singapore-based United Overseas Bank suggests that the country is on a similar path as Japan. In 2017, for the first time in modern Singapore's history, the percentage of people who were 65 years old or older was equal to the share of residents younger than 15.
China's fertility rate keeps dropping despite the government's 2016 decision to allow families to have two children instead of one, so local authorities are taking steps to encourage more childbirth.
About 25 percent of China's population is expected to be 60 years or older by 2030, a significant increase compared to the roughly 13 percent of residents who were part of that age bracket in 2010.