Example of Year-on-year and Cumulative Spreadsheets

To see how these are built up, consider results for a scalar variable x3tot (household consumption) whose percentage-change results for the first 4 years of the base are

2.0 3.0 4.0 5.0 respectively

and whose results for the first 4 years of the policy run are

3.0 3.5 4.7 5.8 respectively.

The year-on-year spreadsheet for the base will show the x3tot results as

2.0 3.0 4.0 5.0

while the cumulative spreadsheet for the base case will show the x3tot results as

2.0 5.06 9.2624 14.7155

[Here, for example 5.06 is obtained by accumulating 2.0 and 3.0.

The result is 100*(1.02*1.03 - 1). Similarly 9.2624 = 100*(1.02*1.03*1.04 -1).]

The year-on-year differences spreadsheet (differences between the policy and base) will show the x3tot differences as approximately

1.0 0.5 0.7 0.8

(that is, approximately 3.0-2.0, 3.5-3.0, 4.7-4.0 and 5.8-5.0) while the cumulative differences spreadsheet will show the x3tot differences as approximately

1.0 1.5 2.2 3.0 (that is, approximately 1.0, 1.0+0.5. 1.0+0.5+0.7, 1.0+0.5+0.7+0.8).

In fact the exact results are slightly different from these since

(a) the year-on-year percentage changes are calculated as percentage changes of the actual year-on-year base values,

(b) the cumulative results are compounded exactly (as for the cumulative results for one run).

For details of the way the cumulative differences results are calculated, see the GEMPACK documentation about GEMPACK program DEVIA in GEMPACK document GPD-4.

URL of this topic: www.copsmodels.com/webhelp/rundynam/hc_yonyexm.htm

Link to full GEMPACK Manual

Link to GEMPACK homepage