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	Partial Budget Analysis	Land Equivalent Ratio
Field	Food Agriculture Studies	Food Agriculture Studies
Family	Process / pipeline	Process / pipeline
Year of origin	1988	1980
Originator	CIMMYT Economics Program	Roger Mead & Roger W. Willey
Type	Marginal partial-budgeting pipeline for a single farm change	Descriptive index of relative land productivity
Seminal source	CIMMYT Economics Program. (1988). From Agronomic Data to Farmer Recommendations: An Economics Training Manual (Completely Revised Edition). Mexico, D.F.: International Maize and Wheat Improvement Center (CIMMYT). ISBN: 9789686127188	Mead, R., & Willey, R. W. (1980). The Concept of a 'Land Equivalent Ratio' and Advantages in Yields from Intercropping. Experimental Agriculture, 16(3), 217-228.
Aliases	Partial Budgeting, Farm Partial Budget, Marginal Budget Analysis, CIMMYT Partial Budget	LER, Relative Yield Total, Land Equivalent Coefficient, Intercropping Land-Use Efficiency
Related	3	4
Summary	Partial budget analysis is a marginal method of farm management economics that evaluates the profitability of a single, well-defined change to a farm plan — adopting a new variety, adding an irrigation, switching a feed ration — without rebuilding the whole-farm budget. Codified for agronomic recommendation work in the CIMMYT Economics Program's 1988 manual From Agronomic Data to Farmer Recommendations, it rests on a simple insight: only the costs and revenues that actually change need to be counted. The analyst arranges those changes into four cells — added revenue and reduced costs on the positive side, reduced revenue and added costs on the negative side — and the net of the two columns is the change in profit attributable to the change alone.	The land equivalent ratio (LER) is the standard index for judging whether intercropping — growing two or more crops together on the same land — uses land more efficiently than growing each crop separately. Formalized by Roger Mead and Roger Willey in 1980, the LER expresses how much land would be required under sole cropping to produce the yields achieved by one unit of intercropped land. It is computed by dividing each component crop's intercrop yield by its sole-crop yield and summing these partial ratios across all components. An LER greater than one means the intercrop is more land-efficient than the corresponding sole crops, and the amount above one quantifies the land saved, giving agronomists a simple, interpretable, and widely used measure of the biological advantage of mixed cropping.