The quality and quantity of population in the country have direct effect on the trade.
Densely populated countries have a lot of local demand. So, there is hardly any surplus for export trade.
The thinly populated countries have limited local demand. Therefore, they have a lot of surplus for trade.
The quality of population also affects trade. More resourceful, enthusiastic and skilled people in the country, more innovative production and trade in the country.
In many countries, skills of a person is preserved from generation to generation. Hence, they are specialised in certain products. Therefore, they develop trade of such goods. For example, carpets in Iran, woollen goods of Jammu and Kashmir, Chinese porcelain, etc.
The standard of living also affects trade. In some countries population is less but due to high standard of living, there is more demand for expensive goods. So, import trade is developed there.