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Di4qFT C C-11"ITT PROFILE (DATA) ELEMENT APPENDIX <br />Linear And Exponential Population Projections: Explanation Of Methodology <br />As prepared by the Orange County Planning and Inspections Department <br />Two extrapolative population projection methods were used: LINAVE or linear extrapolation <br />and EXAVE or exponential extrapolation. <br />The LINAVE method assumes that population will change by identical increments in each <br />interval -of future time and is -calculated :based on the average; population change in decades. <br />This method is considered to be the most accurate method for moderately growing townships, <br />at a rate of up to 25 %. <br />The EXAVE method assumes that population will occur at constant percentage rates over time <br />and is calculated based on the average rate of population change in previous decades. This <br />method is considered to be the most accurate method for rapidly growing townships, at a rate of <br />more than 25 %, and townships with less than 5000 inhabitants.) <br />The equations used in the EXAVE and LINAVE methods are described below: <br />Linear Extrapolation (LINAVE) <br />Pt + n = Pt +[Pt- Pi/(t -i)]n <br />Exponential Extrapolation (EXAVE) <br />Pt + n = Pt [Pt/Pt -i] n/(t -i) <br />Where: P= population <br />t = terminal year of base period <br />i = initial year of base period <br />n = number of years to projected year <br />SOURCE: Andrew M. Issenman . "The Accuracy of Population Projections for Subcounty <br />Areas" Journal of the American Institute of Planners. July 1977. vol 43, No. 3. Pps. <br />247 -259. <br />6 <br />8/16/2007 <br />