An objective measure of overpopulation is population density rather than simply the total population of a nation. The Netherlands has been one of the richest countries of Europe for hundreds of years (roughly measurable by GDP per capita), and it is one of the most densely populated as well, with about 415 people per sq. km. In the last decades we have seen the spectacular rise of Taiwan, Hong Kong and South Korea, countries with very high density of people. Japan has been a very rich nation for several centuries at least, at par with the UK, The Netherlands and Switzerland. All these wealthy countries have the similar population density as India or Pakistan, and if high population density were a bad thing, they wouldn't be rich. To make this argument complete, we must recognize the other side of the spectrum-nations which are rich and sparsely populated, like the US and Canada, with densities of 33 people and 4 people per sq km respectively, which shows that there is no correlation between wealth and population density.
A higher density of people INCREASES their productivity-witness how people live so well in a big city within the same country in comparison to smaller towns or farms. Efficiency of exchange of produce and productivity goes up with proximity. Most humans live in cities for a reason. There's plenty of land left-even if you drive around in Taiwan or Japan you see that most of the country is largely not populated. People prefer to live in buildings and cities, and are not being "cramped" into a city as some land lover anti-urban people claim. People enjoy a better standard of life in big cities-which is why they keep moving to them. Big cities have more of everything in supermarkets and everywhere else you go. Small towns have scarcities.
Northern Europe and now some other countries of Europe are encouraging population growth, which is a good thing for the world. No matter where we live, a thriving nation can always buy things from us, whatever we produce, and it is great to see the number of humans on the planet increasing. The Chileans can sell them more Copper and the US more Starbucks coffee franchises to such a nation.
I do not have numbers from Malthus' times, but it should be clear that despite all his warnings, we have continued to increase in numbers, and in general live better than a few hundred years ago (measure by wealth, the overall consumable goods we have per person). In 1770 approx (data from Adam Smith), the English speaking North America was about 4 Million in population, UK was 8 Million, and France was 24 Million. Look at where we have come today! The United States is 300 Million people, the UK and France are 60 Million, and these countries are far richer today than before, with more consumable goods than those times, and people living much better.
We should stop buying into the false theories of alarmists of overpopulation. We have many more inhabitants than before, and probably will keep on growing-we shouldn't be whining about something which in reality, should be celebrated.
People love to live in high density areas, we are like bees
If you look at the list of countries by population density, as pointed out above, there is no correlation between wealth of the country and it being rich or poor (roughly measurable by GDP per capita). However, even the highest population density nations like Japan, the Netherlands and Singapore are nowhere near the population density of the world's most populous cities-the difference is about 10x! New York City has a density of 10000 people per sq km, and Osaka is about 5000 per sq. km. Japan and the Netherlands overall have a population density of only 400 people per sq km. What's going on?
It is clear that humans love to live close to each other, many times on top of each other as in high rise buildings. The future cities are increasingly vertical. Even the most high density population nations like Japan, India and Netherlands only have 400 people per sq km, clearly there's a lot more room for more people, given that people are living by choice in metro areas like New York City and Osaka, Japan and have population densities which are ten times more than the average density of the entire nation!
In summary, there's no scarcity of land for humanity, and we can increase our population a lot more overall without worrying about overpopulation.