What is the TOA-MD Model? Basic Concepts and an Example

John Antle

Roberto ValdiviaAgricultural and Resource Economics

Oregon State University

www.tradeoffs.oregonstate.edu

What is the TOA-MD Model?• The TOA-MD Model is a unique simulation tool for multi-dimensional impact assessment that uses a statistical description of a heterogeneous farm population to simulate the adoption and impacts of a new technology or a change in environmental conditions. • TOA-MD is designed to simulate what would be observed if it were possible to conduct a controlled experiment. In this experiment, a population of farms is offered the choice of continuing to use the current or “base” production system (System 1), or choosing to adopt a new system (System 2).• In fact it is never possible to carry out such ideal experiments, so TOA-MD is designed to utilize the available data to attain the best possible approximation, given the available time and other resources available to conduct the analysis. • Additionally, TOA-MD is designed to facilitate analysis of the inevitable uncertainties associated with impact assessment.

• There are two components in the TOA-MD analysis: • First, the model simulates the proportion of farms that would adopt a new system (system 2), and the proportion that would continue to use the “base” system (system 1) • Second, based on the adoption rate of the system 2, the TOA-MD model simulates selected economic, environmental and social impact indicators for adopters, non-adopters and the entire population.

• How is the TOA-MD simulation approach related to the experimental and non-experimental statistical approach to impact assessment (estimation of “treatment effects”)?

• The underlying conceptual model is very similar: economic agents (farms in this case) self-select into “treatment” or choose to adopt a technology (or adapt to an exogenous change such as climate change), and related “outcomes” occur to those self-selected into “treatment” (adoption)• For “ex post” assessment the simulation approach can be used together with experimental methods to parameterize the model and simulate outcomes of interest, including both “mean” indicators and other “threshold” indicators such as poverty rates and indicators based on other quantifiable outcomes. It can also be used to simulate “policy relevant” effects, such as technology adoption induced by payments for ecosystem services. • For “ex ante” assessment, where statistical methods cannot be used, the simulation approach provides a “laboratory” to explore potential impacts, using various types of available data to construct the future “counterfactual,” e.g., the impacts of and adaptation to climate change.

TOA-MD approach: modeling systems used by heterogeneous populations

Systems are being used in

heterogeneous populations

A system is defined in terms of household, crop, livestock and

aquaculture sub-systems

(ω)

0

Map of a heterogeneous region

Opportunity cost, system choice and adoption

Opportunity cost = v1 – v2

follows distribution ()v1 = returns to system 1V2 = returns to system 2 System 1: > 0

(non-adopters) System 2: < 0

(adopters)

opportunity cost

• Outcome distributions are associated with system choice– Farms select themselves into “non-adopter” and “adopter” sub-

populations, generating corresponding outcome distributions for these sub-populations

• Impact indicators are based on system choice and outcome distributions– TOA-MD produces mean indicators and threshold-based

indicators• Analysis shows that impacts depend on the correlations

between adoption (opportunity cost) and outcomes– Many impact assessments ignore correlations– Yet these correlations are often important for accurate impact

assessment!

Adoption, Outcome Distributions and Impact Indicators

Adoption and outcome distributions

Entire Population with adoption: 55% >

r(1,a)% non-adopters

System 1: 20% >

System 1 before adoption: 25% > threshold

System 2: 90% >

Outcome z

(z|1)

r(2,a)% adopters (z|1,a) (z|2,a)

(z|a)

Components of TOA-MD Analysis

System characterization

Adoption rate

Population (Strata)

Impact indicator design

Opportunity cost distribution

Outcome distributions

Indicators and Tradeoffs

Design

Data

Simulation

An Example: Integrated Agriculture-Aquaculture• Based on Dey et al (2010) Agricultural Economics: economic analysis of IAA• stratified survey of farms, without and with IAA

• Design of TOA-MD analysis• population: farm households in southern Malawi where aquaculture is

feasible• strata: 5 southern districts• systems:

• Subsistence crops• Crops + aquaculture, low or high integration

Subsistence crops

Aquaculture

Irrigated vegetables

-1000

-800

-600

-400

-200

0

200

400

600

800

0 10 20 30 40 50 60 70 80 90 100

Opp

ortu

nity

Cos

t

Adoption Rate (%)

Zomba Mwanza Mulanje Thyolo Mangochi

Adoption Rate and Opportunity Cost of Adopting IAA in Southern Malawi – Predicted Adoption Rate is Point Where Curves Cross the

Horizontal Axis

Poverty Rate and Adoption Rate of IAA, Southern Malawi

60

65

70

75

80

85

90

95

100

0 10 20 30 40 50 60 70 80 90 100

Pove

rty

Rate

(%)

Adoption Rate (%)

Zomba Mwanza Mulanje Thyolo Mangochi

Mean Monthly Protein Consumption and Adoption of IAA, Southern Malawi

0

0.5

1

1.5

2

2.5

0 10 20 30 40 50 60 70 80 90 100

Mea

n M

onth

ly P

rote

in C

onsu

mpti

on p

er p

erso

n (k

g)

Adoption Rate (%)

Zomba Mwanza Mulanje Thyolo Mangochi

Note most improvement occurs for those districts with lowest

protein consumption

Relationship between adoption and Protein Consumption, Non-adopters and Adopters of IAA, Mulanje Dist., Malawi

Non-adopter sub-population and entire

population are equal at 0% adoption

Adopter sub-population and entire population are equal at 100% adoption

Slope of relationship between indicator and adoption rate has

same sign as the correlation between opp cost and the

outcome variable (negative in this case)

Relationship between adoption and Mean Returns per Farm, Non-Adopters and Adopters of IAA, Mulanje District, Malawi

Economic outcomes that are positively related to net returns have a maximum in the entire population at the

predicted adoption rate (41% in this example)

-1000

-800

-600

-400

-200

0

200

400

600

800

0 10 20 30 40 50 60 70 80 90 100

Op

po

rtu

nit

y C

ost

Adoption Rate (%)

Zomba Mwanza Mulanje Thyolo Mangochi

The various “treatment effects” discussed in the experimental and non-experimental statistical literatures are either equivalent to or closely related to the mean indicators generated by the TOA-MD model:

• AveTreatment Effect = mean population indicator• Marginal Treatment Effect = change in mean indicator• Treatment on Treated = related to mean indicator of adopters• Treatment on Untreated = related to mean indicator of non-

adopters• Policy relevant treatment effect = derived from mean

indicators

Ave. farm income ($/year) Poverty rate (%)

Mean Monthly Protein Consumption (kg/person)

Strata Adoption rate (%)

base (no adoption)

% Change on

population

% Change

on adopters

base (no adoption)

% Change on

population

% Change

on adopters

base (no adoption)

% Change on

population

% Change

on adopters

ZOMBA 49.22 112.47 54.60% 135.62% 87.50 -15.81% -42.48% 1.41 12.86% 38.95%

MWANZA 49.40 89.01 50.77% 137.61% 99.16 -16.01% -51.88% 1.94 0.30% 10.64%

MULANJE 40.81 81.01 54.46% 179.51% 84.30 -11.38% -44.26% 0.65 53.10% 191.35%

THYOLO 41.92 170.85 41.85% 116.92% 95.93 -16.48% -56.11% 1.75 -0.49% 28.63%

MANGOCHI 37.95 188.62 30.77% 116.63% 72.24 -10.53% -53.66% 0.77 56.42% 178.33%

REGION 44.49 123.90 45.23% 132.70% 87.11 -11.25% -30.45% 1.29 15.32% 59.00% 1

Summary: Impacts of IAA Adoption on Farm Population and IAA Adopters

Conclusions• TOA-MD is a unique simulation tool for multi-dimensional impact assessment of agricultural systems• The Malawi case study illustrates how it can be used with available data to simulate:

• the adoption rate of a new technology• the economic, environmental or social impacts of the new technology

• The model can also be used for analysis of ecosystem services, and impacts of climate change and other environmental change• Training in use of the model, and the model software are available from the TOA Team.

• More info is available at : http://tradeoffs.oregonstate.edu