Population size defines a state's identity, along with determining culture, economic indicators, and sometimes even international authority. As much as some countries hold high population sizes, others remain some of the least populated and provide different characteristics due to their few people.

Our focus is biased toward the most ten populated countries in the world; however, we will also include some of the least populated nations to give an indication of the demographic disparities around the world.

China is the most populous country on Earth, with over 1.4 billion people on its vast area. The country harbors different ethnic groups, languages, and cultural traditions of its own. Highly populated cities like Beijing, Shanghai, and Guangzhou contribute terribly towards the growth and urbanization of this country.

Not too far behind is India, with 1.4 billion citizens. In fact, the cultural variety in India provides the contrasting demography with a rather young population and serious impetus on economic growth. Its major cities of Mumbai, Delhi, and Bengaluru are very much on the ascendance, both as economic and technological hubs.

It has been ranked the third country in the world; it has hosted more than 330 million with its 50 states. Alternatively, the population may be very much concentrated within cities like New York City, Los Angeles, and Chicago.

Immigrants in the last decades have also been at a better position of adding to the American population. This has enriched the population with cultural diversity and dynamism in the workforce.

4. Indonesia

Indonesia is the largest country within Southeast Asia, with most of the Muslim-populated countries, at over 273 million persons. Being an archipelago, it includes over 17,000 islands. Actually, this kind of geography would be very well concentrated in areas around such cities as Jakarta, Surabaya, and Bandung, but highly dispersed across those numerous islands. It is a key regional economic power with a young and growing population.

With more than 240 million citizens, Pakistan is the fifth most populous country in the world. It is still a developing country and faces huge problems both in education and healthcare because of the economic instability.

Populations are highly concentrated in such urban areas as Karachi and Lahore. Because of the country's strategic location, which has potential for economic development, it is of great importance to South Asia.

Brazil is the most populous country in South America, hosting over 215 million people. The reason for this rich biodiversity that has endowed Brazil can be attributed to the Amazon rainforest. There is huge concentration in the urban areas of São Paulo and Rio de Janeiro, contributing to a very lively culture known all over the globe.

Being the most populous country in Africa, Nigeria keeps a population of over 218 million citizens. The high birth rate leads to rapid urbanization and simultaneously inflicts heavy pressure on cities such as Lagos, Abuja, and Kano. Such heightened growth in youth comes with correspondingly formidable opportunities and challenges exerted upon health care, infrastructure development, and employment provided for its citizens.

This would classify it as one of the most densely populated countries in the world, with over 173 million Bangladeshis. If this were the case, there would have to be growth consideration for burgeoning cities like Dhaka, considered among some of the fastest-growing urban centers in the world, with such a small amount of land area.

Success stories for Bangladesh include tremendous economic growth, a boost in poverty reduction, but some challenges still persist related to high population density and climate change concerns.

Of all of the most populous countries it covers almost three times the area of China, and is less densely populated having a total population of approximately 146 million. Though the overall population of Russia is concentrated west of the Ural Mountains, its major cities are filled with residents including Moscow and St. Petersburg. Low birth rates and emigration have constricted Russia's population growth.

Rounding out the top ten is Mexico, with a population of about 131 million. Many Mexicans live in urban areas, most significantly in the capital city of Mexico City, which remains one of the most populous metropolitan areas in the world. Recently, Mexico has been experiencing a slowing in their population growth; however, it remains as one of the largest cultural and economic powers in Latin America.

Such heavy populations highly contribute towards the global economy, culture, and technological advancement. As much as these countries face special challenges, they concurrently have opportunities pertaining to infrastructure, resource management, health care, and education. With the shifting trends in population across the globe, such populous nations keep adapting to the demands of a growing citizenry.

At the opposite extreme end of the spectrum, some countries are very lightly populated. Most are marked by tight-knit communities, low levels of urbanization, and special preserves: ecological and cultural. The following are 15 of the countries with some of the world's smallest populations:

1. Holy See

2. Tuvalu

3. Nauru

4. Palau

5. San Marino

6. Monaco

7. Liechtenstein

8. Saint Kitts and Nevis 

9. Marshall Islands

10. Dominica

11. Saint Vincent and the Grenadines

12. Antigua and Barbuda

13. Seychelles

14. Andorra

15. Micronesia

These are those countries which, notwithstanding their reduced population size, assume great relevance at the regional level of diplomacy and tourism and quite often depict high living standards.

Others contain international hubs or offer unique ecological sanctuaries, and thus these prove that population is not a building block to the global significance of a country.

Huge diversities in populations point to different paths taken toward development and identity within each separate country. Whereas the most populous countries in the world have to work at bettering themselves with the constant challenges of urbanization, resource allocation, and economic growth, smaller nations provide a great deal of cultural and environmental value.

The dynamics that keep changing within the globe to date have the populous and sparsely populated countries continuing their contributions to the ever-changing tapestry that is our world.