The chart shows the development of three companies from 1990s to 2000s in the area of making refrigerators.
From 1990 to 2000, the time for three companies to make a refrigerator all declined. Company A and Company C declined more sharply than Company B. So from 1990 to 2000 the rank of which company use more less time making refrigerators changed significantly. We can expect that the efficiency of company C will surpass that of Company B after two years.
In 1990, Company A and Company C needed 30 hours and 35 hours. Ten years later, Company A spent more than 22 hours making a refrigerator and Company C used less 30 hours to make a refrigerator.
But the variation for Company B was not very obvious. From 1990 to 2000, the time Company B needed to make a refrigerator decreased only slightly, from close to 25 hours to closer 25 hours but not over 25 hours.
