
GROSS PRIVATE DOMESTIC INVESTMENT: Expenditures on capital goods to be used for productive activities in the domestic economy that are undertaken by the business sector during a given time period. This is the official item in the National Income and Product Accounts maintained by the Bureau of Economic Analysis measuring capital investment expenditures. Gross private domestic investment tends to be the least stable of the four expenditures, averaging between 1218% of gross domestic product.
Visit the GLOSS*arama




ARC ELASTICITY: The average elasticity for discrete changes in two variables. The distinguishing characteristic of arc elasticity is that percentage changes are calculated based on the average of initial and ending values of each variable, rather than initial values. Arc elasticity is generally calculated using the midpoint elasticity formula. The contrast to arc elasticity is point elasticity. For infinitesimally small changes in two variables, arc elasticity is the same as point elasticity. Arc elasticity is best considered the average elasticity over a range of values for a relation. Like any average, some values within the range are likely to be greater and some less. However, it provides a quick approximation of elasticity when more precise and sophisticated calculation techniques are not possible.Working Through an ExampleA Standard Demand Curve 

 The demand curve displayed to the right can be used to illustrate the measurement of arc elasticity using the midpoint elasticity formula. If the price declines from $12 to $8, the quantity demanded increases from 4 to 6, from point X to point Z. Using this midpoint formula (with price designated as P and quantity designated as Q) average price elasticity of demand is:midpoint elasticity  =  (Q[Z]  Q[X]) (Q[Z] + Q[X])/2  ÷  (P[Z]  P[X]) (P[Z] + P[X])/2 
midpoint elasticity  =  (6  4) (6 + 4)/2  ÷  (8  12) (8 + 12)/2  =  (2) (5)  ÷  (4) (10) 
midpoint elasticity  =  0.4  ÷  0.4  =  1.0 
Ignoring the minus sign, the price elasticity of demand over this segment of the demand curve from X to Z is 1.0.An Average ValueThis value of 1.0 is actually an average for the entire range between points X and Z. Precise estimates of point elasticity shows that the elasticity is 0.67 at point X and 1.5 at point Z. Moreover, the elasticity is different at each point on a straight line demand curve such as this one. The only point in which the elasticity is exactly equal to 1.0 is at point Y, the midpoint between X and Z.This last observation is worth emphasizing. The midpoint elasticity formula effectively estimates the point elasticity at the very midpoint of the overall segment. This means that the elasticity of any point on a demand curve (point elasticity) can be obtained by calculating the arc elasticity with the midpoint elasticity formula such that the desired point is dead center in the middle, the midpoint of the arc.
Recommended Citation:ARC ELASTICITY, AmosWEB Encyclonomic WEB*pedia, http://www.AmosWEB.com, AmosWEB LLC, 20002019. [Accessed: January 20, 2019]. Check Out These Related Terms...       Or For A Little Background...       And For Further Study...      
Search Again?
Back to the WEB*pedia



PINK FADFLY [What's This?]
Today, you are likely to spend a great deal of time browsing about a thrift store seeking to buy either a desktop calendar with all federal and state holidays highlighted or a halfdozen helium filled balloons. Be on the lookout for pencil sharpeners with an attitude. Your Complete Scope
This isn't me! What am I?


Junk bonds are so called because they have a better than 50% chance of default, carrying a Standard & Poor's rating of CC or lower.


"Act well at the moment, and you have performed a good action for all eternity."  Johann Kaspar Lavater


JEH Journal of Economic History


Tell us what you think about AmosWEB. Like what you see? Have suggestions for improvements? Let us know. Click the User Feedback link.
User Feedback

