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Threshold 21 Model
Threshold 21 iSDG Model
MEG Model
M3 Model

Threshold 21 (T21) is a dynamic simulation tool designed to support comprehensive, integrated long-term national development planning.  T21 supports comparative analysis of different policy options, and helps users to identify the set of policies that tend to lead towards a desired goal.  This insight into how different indicators of development interact with one another to produce an outcome deepens users understanding of development challenges.

T21 was developed from more than 20 years of extensive research and application carried out in consultation with the World Bank, UN agencies, developing country governments, and non-governmental organizations.

T21 is transparent, collaborative, interconnected, robust, and customizable, and includes many critical features that support an inclusive, comprehensive, and integrated development planning process.  Models that are customized for countries are based on the "T21 Starting Framework", a set of interconnected sectors combined into a rigorous macroeconomic framework. The sectors and their interrelations represent the fundamental mechanisms that are responsible for socio-economic development.


What Can T21 Do?

The most important application of T21 is contributions to the national planning process: once a country identifies its vision, and key goals are determined, T21 generates scenarios describing the future consequences of the proposed strategies.

Broadly, T21 is an especially useful tool for preparing Poverty Reduction Strategies that emphasize the Millennium Development Goals (MDG), and for monitoring progress towards the MDGs or other national goals. More specifically, T21 supports stakeholder consultations, preparing strategy documents that address sectoral or industrial interests, preparing data and analyses for loan negotiations, and monitoring and evaluating national plans.

To date there are more than 15 unique, customized T21 models with applications in less-industrialized countries such as Malawi, Mozambique, and Bangladesh, and industrialized countries such as the United States and Italy. MI builds local capacity for use of T21 for through an intensive, multi-year training process to assure full appropriation of the model.


Click here to read about country applications of T21.



There are two fundamentally different types of models in existence today. The first group of models predicts the exact outcome of a scenario.  These models are unable to display the process through which they reached their results.  The inability to see through the modeling process makes it difficult to use these models in policy development. 

Transparent models, on the other hand, have causal tracing capabilities, which makes them useful for planning policies. For example, a country may have a policy that it wants to test before adopting it. To test the results, data and the policy are entered into the model. Next, the scenario is simulated and users view and analyze the results. If the results are not what the user wants, the user can look at the simulation process and determine which variables influenced the unwanted outcome.  The variables can then be incorporated in the policy, and the simulation is repeated until the desired outcome is achieved.



T21 facilitates participation and consensus-building by encouraging open consultations with diverse stakeholders and external development partners under a common framework and an easy-to-understand interface. In every country where T21 has been applied, a diverse group of experts from government, private sector and civil society, worked closely with MI modelers to determine the country's vision and goals for the future. The diversity of the groups helps to ensure that all stakeholders share the vision for the future.



T21 is built on the philosophy that national planning is an integrated process, in which planners must consider the economic, social and environmental variables that influence sustainable development. Economic growth, for instance, requires a healthy workforce. Likewise, a healthy workforce requires adequate investment in social services.  If planning does not recognize the links between economics, society, and the environment, unexpected and unwanted policy consequences can result and cause a country to move away from its vision rather than toward it.

The T21 model takes into account over 800 variables and their interdependencies in its simulation.



T21 models are validated through a variety of tests, including the effective simulation of historical data and project up to 30 years into the future.



T21 is built from a "T21 Starting Framework" that represents the broad relationships of socio-economic development.  However, T21’s modular design allows for the modification of any sector, which makes it customizable to unique country situations.

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