Adding exogenous forecasts to scenarios in IFs

Introduction

In addition to constructing scenarios, users can also override model forecasts in a scenario with exogenous forecasts for specific variables. For overriding model forecasts, the user would have to make changes to specific access files and make use of two controllable parameters (All these changes are described in detail below). At this time, the main use of exogenous series in the model is for the work related to the Shared Socioeconomic Pathways (SSPs).

IFs can read in exogenous series for a select number of variables that are normally forecast endogenously in the model. The table below describes all of the variables that can be overridden with exogenous values. When activated, the exogenous forecasts will override calculations within the model. Note that this includes, overriding any values in the first year of the model run and if the exogenous series does not have data for a particular country for a particular year, the endogenously calculated variable is used.

The table does not include the variable GDP at MER. Note, that the model uses exogenous forecasts of GDP per capita at PPP and exogenous forecasts of population and a conversion ratio (PPPCONV) to compute a forecast of GDP at MER which would be similar to an exogenous forecast.

Variables that can be overridden with exogenous forecasts	Description
POP	Population
BIRTHS	Total number of births
DEATHS	Total number of deaths
TFR	Total fertility rate
POPURBAN	Urban Population
EDYRSAG15	Education years obtained by population older than 15 years (Male, Female and Total)
EDYRSAG25	Education years obtained by population older than 25 years (Male, Female and Total)
GDPPCP	GDP per capita at PPP
Migrater	Migration rate (net) as a percent of the population