Falling birthrates have been in the news lately. Some countries are facing an extinction event, especially in eastern europe.
Here is a look at how the number of births have changed country by country:
United Kingdom
1945: 795,868 live births
2017: 774,835 live births
So not much change over time. The population is increasing mainly because people are living longer, plus immigration.
United States
1945: 2,858,000 live births
2017: 3,883,139 live births
As you can see they've had a huge surge over time (35% increase). This is a big part of why the American population has increased since 1945 (the other reasons being increased life expectancy and immigration).
France
1945: 645,899 live births
2017: 729,800 live births
So live births have increased by about 13% over time (with big increases in the 1950's and 1960's before falling back slightly). France is projected to have the biggest population in Europe by mid century, in part because they've maintained their birth rate and also because of immigration.
Germany
1945: 1,060,000 live births
2016: 792,131 live births
Germany is shrinking (deaths have outnumbered births since 1972). They've made up for it by importing temporary workers from the rest of the EU, and in 2015 also accepted 1 million migrants from the Middle East and Africa.
Japan
1945: 1,685,583 live births
2017: 941,000 live births
Japan's population is also shrinking. But they appear to be coping because hardly anyone emigrates and they are still very numerous (their population is currently 125 million).
China
1950: 20,232,000 live births
2017: 17,230,000 live births.
In the 1960's births reached 27 million a year in China. There has obviously been a steep drop since then, but when compared to 1950, they are stable.
India
1950: 16,832,000 live births
2017: 27,271,000 live births
India has the most live births in the world - their population is due to explode, especially if life expectancy increases.
Poland
1947: 630,000 live births
2017: 401 982 live births
Poland has had a 35% drop in births over time. They are also experiencing record emigration and practically no immigration. This might explain why they are so nationalistic - if these trends continue, they face an extinction event, and fears of that always provoke nationalism.
Russia
1946: 2,546,000 live births
2017: 1,690,307 live births
Russia has experienced a 34% drop in births, and in the mid 1990's births fell as low as 1.2 million. They are facing a population collapse, and will likely not be able to hold onto all their territory (especially in the east, where Chinese migrants are moving north to farm - Siberia was captured from the Chinese in the mid 19th century and China's superior demographics and finances mean they are likely to to take it back by mid century).
Russia's collapsing demographics are probably the reason they are so nationalistic at the moment. They not only have no way of matching the United States in population and wealth, but they too face an extinction event if current trends continue.