A horizontal line has zero slope

   Before we leave linear relationships, we need to consider two special kinds of linear relationships that come up in economics from time to time. To the right we show a graph of a linear relationship that is a straight, horizontal line. Such a line has a slope of zero. As we move to the right from point A to point B, Q increases from 10 to 24, but P remains unchanged at 12. So, the rise is zero, even though the run is 14. When we compute rise ÷ run for any two points on this graph the answer will always be zero since the rise will always be zero. Therefore, the Slope = 0.

    This graph shows that P and Q are not related; P remains fixed at a value of 12 regardless of the value of Q.

Copyright © 1995-2004 OnLineTexts.com, Inc. - All Rights Reserved