Human Population Growth
These are the top 10 countries with the fastest population growth rate as of January 1st, 2018.
South Sudan 
On average, South Sudanese women have around 4.9 children. Also, due to the internal conflict, many women are raped, and don't have access to contraceptives. The South Sudanese government is also spending a lot more money on militarism, and not on health care. Also, due to hardship (civil war and infant mortality rates - 105 per 1000 births) many women will have more children, hoping that more will survive.
3.83%
Angola
In Angola, on average, a women will have 5.7 children. Around 47.8% of women, from ages 15-19, are pregnant. Only around 14% of women in Angola use contraceptives, which brings the population up (compared to around 90% of females in the US who have used contraceptives).
3.52%
Malawi
The main factor that contributes to Malawi's high population growth is fertility rate. Similar to the situation in Zambia, the uneducated have around three times the number of children than that of the educated. A reason why Malawi has a high fertility rate is due to too less of the population using contraceptives. According to projections by the UN, Malawi's population is expected to grow to 41.2 million by 2050.
3.51%
Burundi
On average, a woman in Burundi will have about 5.6 children. If fertility and mortality rates don't decline, Burundi's population growth rate is expected to reach 28 million by 2040! The big issue is that Burundi doesn't have enough resources to support their growing population; currently, they consume double the amount of food that they produce.
3.25%
Uganda
Every day, Uganda receives about 2000 immigrants. There are many settlements for refugees being built. About one million people flee from South Sudan from the civil war into Uganda. The Ugandan Government also has an open door refugee policy, so many immigrants and refugees will go to Uganda.
3.2%
Niger
Niger has one of the highest fertility rates in the world, with a rate of 7.6. Some projections believe that the population will triple to 55 million by 2050. In Niger, there also is a poor access to contraceptives. Another factor is that because the men are polygamous, the women try to outdo another in child births.
3.19%
Mali
A projection for the population of Mali in 2050 is 45 million. Without outside help, Mali is in trouble. This is because in a male-dominated society, women don't have much education. But even a little education on how many children one should have and spacing out when your next children will be born can really impact the population growth rate.
3.02%
Burkina Faso
The average fertility rate for Burkina Faso is 5.7. This high fertility rate can be the result of a lack of development; a family can choose to limit the size of their family if they have the resources to do so. The alternative is having a lot of kids, and hoping that a couple will survive.
3%
Zambia
Zambia's population growth is mainly due to a high fertility rate. On average, a Zambian women will have 6.2 children. In Zambia, on average, the poorer population, with little to no formal education, will have more than eight children, while the population with a formal education, and wealthiest 20% have under four children.
2.93%
Ethiopa
In 2017, the UNHCR stated that 850,000 refugees from countries bordering Ethiopia now live in Ethiopia. A factor that may cause refugees to choose Ethiopia as a temporary (or maybe permanent) homeland is that refugees in Ethiopia have access to education. Ethiopia receives refugees on a daily basis, and tries to not turn them away.
2.85%
One of the main causes for high population growth is a high fertility rate. Some of the reasons for high fertility rates are a lack of contraceptive use, medical care, under-development, and the inability to support a family. Some countries understand that this high rate of population growth can have drastic impacts, so they take action. For example, Burkina Faso's government has now allocated 5% of national funds to cut down birth rates. Also, donors are a big help to countries in need; they can supply food, and medical help. Education about family planning can also help to slow population growth.
These are the lowest 10 countries with the slowest (negative) population growth rate as of January 1st, 2018.
Estonia
Many people leave Estonia and go to countries in Europe, because the wages are higher. Many will migrate to Finland (80km away) because salaries are about three times higher than the salaries in Estonia, but the living costs are very similar. Also the low job opportunities and sparse education are another factor for migration. Some residents live in debt because of their low paying job, but can't switch professions due to the basic education.
-0.57%
Bulgaria
One reason behind Bulgaria's decreasing population is due to the fertility rate. A lot of the Bulgarian Population is quite old, and unable to reproduce. Another factor is migration. Due to this, Bulgaria has been losing people at a pretty fast rate.
-0.61%
Moldova
Moldova has a very low pay rate compared to the minimum wage needed to survive. Due to this, many residents will emigrate out for economic reasons. Because of this economic disaster, many people also don't want to go back to Moldova.
-1.05%
Latvia
Due to Latvia's association with the EU, 20% of the nation has left to work in wealthier countries. This economic migration is one of the big reasons why Latvia's population is declining. Many people in Latvia have extremely low wages, so it's no wonder why some people would choose to emigrate out.
-1.08%
Lithuania
Ever since the change from communism to capitalism, the population started decreasing. People were raised to live like a communist, and when Lithuania turned capitalist, very little people knew what to do. Also, many criminal gangs and mafia were present. This political instability lead many people to emigrate out of Lithuania. Many of these immigrants will emigrate to the EU, which has better prospects for the future.
-1.08%
Saint Pierre and Miquelon
Ever since the 1920's, the population has been declining. After the prohibition of alcohol, their economy has been going down-hill. Currently, their economy is based on fishing, but Saint Pierre and Miquelon and Canada are having disputes over fishing quotas. Also, to get an education at a university, inhabitants must travel to other places to get their formal education.
-1.08%
Lebanon
Lebanon is quite small, so many Lebanese are forced to live elsewhere. About 15 million Lebanese people live outside of Lebanon, and around 4.1 million live inside. Many who wish to return can't, as the country isn't big enough to support all those people. Also because Brazil (which houses around 7 million Lebanese) has a lot of Christians, many Christian Lebanese will emigrate to Brazil to flee religious persecution.
-1.1%
American Samoa
In American Samoa, regardless of population, resources will continue to decline. They depend heavily on imported goods, sometimes up to thousands of miles away! This means that prices for foods can get pretty high. As a result, as of 2017, about 26 to 27 people per 1000 leave American Samoa every year.
-1.3%
Puerto Rico
Puerto Rico's population has been decreasing because many Puerto Ricans will migrate to the states (primarily Florida). Since Hurricane Maria, 239,000 Puerto Ricans moved to the US. This really affects Puerto Rico, because it leaves its economy damaged. If the Puerto Ricans move back, they will find the economy being worse than it was when they left.
-1.74%
Cook Islands
Cook Islands' population has been decreasing because Cook Islanders have New Zealand citizenship. Cook Islanders also have a major disadvantage for economic oppurtunities. This causes many islanders to migrate to New Zealand. Also, the fertility rate has been decreasing over the years.
-2.79%
One of the main reasons for a decreasing population is emigration to other countries. This is partly due to an unsustainable economy and/or government. Many countries nearby (or in some cases, far away) offer better opportunities for living, such as higher wages, but similar living costs.