# Agriculture¶

## Purpose and Perspective¶

Agriculture production in iSDG includes crops production, fishery production (separating fish catch and harvest - aquaculture), livestock production and forestry production.

Crops production is influenced by the harvested area, and soil nutrition (with the availability of macro-nutrients N, P and K represented), precipitation, irrigation, which along with total factor productivity affects the actual yield [1]. Production factors are combined as in a Cobb-Douglas production function. Factor productivity depends on several other drivers, including: education (average years of schooling used as proxy); health (life expectancy used as proxy); infrastructure (including roads and irrigation infrastructure); access to electricity; level of governance; macroeconomic stability (inflation rate used as proxy); openness to trade; and public agriculture expenditure. More specifically, an increase in the production factors or their productivity reduces the difference between actual and attainable yield.

Livestock production is affected by the same factors described above for crops. However, in the case of livestock, production per unit of land does not converge to a maximum attainable yield, but its growth is determined directly by growth in driving factors and the corresponding elasticity parameters.

Fish capture is also affected by the same factors described above for crops. However, in the case of fishery, we do not consider a maximum yield based on soil and climate factors, but production is limited by the availability of fish resources (stocks). Fish harvest (farming), separately represented in the model, does not depend on the availability of fish resources.

In the production functions described above, growth in production is driven by the increase in availability of the necessary production factors or by the increase in their productivity. This implies that demand factors are not considered in the calculation of production, that the quantities produced are fully consumed, and prices are exogenous to the model. Such production function can adequately represent the long-term pattern of production growth, and is therefore well suited to calculate production in iSDG. On the other hand, the production functions used are not suitable to represent short-term fluctuations in production caused by the accumulation of inventories of finished goods. Since iSDG is geared toward the analysis of long-term trends and not short-term fluctuations, these limitations do not affect the validity of the model.

## Exogenous Input Variables¶

• Crop Intensity Index - Units: Dmnl

• Crop Production Value Per Ton - Units: RLCU [17]/Ton

• Livestock value added per ton – Units: RLCU/Ton

• Fish Catch Production - Units: RLCU/Year

• Fish Harvest Production - Units: RLCU/Year

• Forestry Production - Units: RLCU/Year

• Other agriculture input cost per ton of production – Units: RLCU/ton/Year

• Effect of change in type of crop on yield – Units: Dimensionless

## Initialization Variables¶

• Initial crops production – Units: RLCU/Year

• Initial yield - Units: Ton/(Ha*Year)

• Potential yield - Units: Ton/(Ha*Year)

• Initial livestock production – Units: RLCU/Year

• Initial livestock production per hectare – Units: RLCU/Year/Ha

• Initial agriculture capital output ratio – Units: Year

## Modeling Details¶

Agriculture production calculated in this sector includes crops production (further separated to cereals and other crops by way of the subscript [crop]) and livestock production. Further separation among crops can be introduced as needed by expanding the [crop] subscript (and the underlying database).

In iSDG the production factors are used in unit-consistent form, using the values for capital, labor, and land relative to their initial values, or normalized. A similar approach is used to normalize the drivers of productivity. Thanks to such normalization, the effects of production factors and drivers of productivity are effectively and consistently combined. More specifically all such effects are combined in a multiplicative form, assuming Hicks-neutral technological change.

Finally, the yield gap ratio (i.e. attainable yield minus actual yield over attainable yield) is calculated as:

$$Y = \frac{Y^{crop}_{init}}{TFP_{crop}*K_{crop}^{k}* L^{l_{crop}}}$$

Where

• Y is the yield gap ratio

• TFP is total factor productivity

• K is the relative capital per hectare

• k is the capital elasticity

• L is the relative employment per hectare

• l is the labor elasticity on yield

• Different crop types are represented in the model (in the core model, cereals and other), and the initial value is the model start year.

## Footnotes and References¶

[1] The yield structure is not explicity captured in the simplified diagram, but is simply the crops production divided by the harvested area.

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[17] Real local currency unit, with base year chosen based on the country’s most commonly used base year.