Comparing the sizes of countries is more complicated than you might think. The main problem is that the figures provided by different sources such as the United Nations and the Central Intelligence Agency often disagree with one another.
There are several reasons for this disagreement. For one thing, country size can be measured either as total area or as land area. Total area measurements include area covered by inland bodies of water such as lakes, reservoirs, and rivers. Land area measurements exclude these bodies of water.
Secondly, some sources compute a country's size by adding up the sizes of all of its internal political areas, such as states, provinces, or republics. Figures computed this way are likely to differ from figures computed using other methods.
A related issue involves disputed areas and political claims. Some sources might include these areas as part of a country's size while others might not. This issue is especially relevant in the case of China, which has several disputed areas along its borders.
Determining the size of China is further complicated by a couple of other factors:
Given all of these factors, it's not surprising that different lists of the largest countries in the world don't always agree with each other. Below are two different lists of the largest countries, based on data from the CIA World Factbook. The first list ranks the countries by land area and the second ranks them by total area (including inland bodies of water).
- There isn't reliable, detailed statistical information available for the country.
- Figures provided by some sources might include Hong Kong and Macau (two territories returned to Chinese control within the past 10 years) while figures from other sources might not.
Total Area (including inland water)
- Russia - 6,562,116 sq. miles
- China - 3,600,947 sq. miles
- United States - 3,537,439 sq. miles
- Canada - 3,511,023 sq. miles
Notice how China, the United States, and Canada trade positions relative to one another between these two lists, just as China and the United States do in the lists that you refer to in your question.
- Russia - 6,592,772 sq. miles
- Canada - 3,855,103 sq. miles
- United States - 3,794,083 sq. miles
- China - 3,705,407 sq. miles
(Question submitted by a 7th-grade teacher at Central Middle School in Nebraska. )