Shock and changes are expressed as changes to the price and/ or production of any produced or traded item in the reference data.
A simple model is deliberately used to ensure that the user has an intuitive understanding of the calculations. Simulations are used to develop a narrative about the connection between a shock or other change in which the uncertainties about the values used e.g future food and crop prices, are explicitly declared and which is comprehensible to non-technical users and open to challenge.
HEA is described as an approach rather than a method because it is a framework which defines the minimum information required and a way of analyzing this. The quality of the data required depends on the objective of the assessment and the acceptable quality of output.
two quantitative reference data sets are in use