Rarely one will see a row of numbers on the third side. This means there's a the third line on the graph which represents a [[phenomenon]] that cannot be measured with the same units. The phenomena are related, but they are really different topics. Take, for instance, a graph which shows the [[GDP]] (Gross Domestic Product) of the [[U.S.]], and the second line showing the the GDP of China. A third line could represent the population of [[China]]. Because GDP is measured in different units than population, you need to use the third side of the graph. This would measure population. This way one can compare the population to GDP using the same intervals of time. | Rarely one will see a row of numbers on the third side. This means there's a the third line on the graph which represents a [[phenomenon]] that cannot be measured with the same units. The phenomena are related, but they are really different topics. Take, for instance, a graph which shows the [[GDP]] (Gross Domestic Product) of the [[U.S.]], and the second line showing the the GDP of China. A third line could represent the population of [[China]]. Because GDP is measured in different units than population, you need to use the third side of the graph. This would measure population. This way one can compare the population to GDP using the same intervals of time. |