Population - IFs

Note: The documentation of IFs is 'under review' and is not yet 'published'!

Model Documentation - IFs
Macro-economy - IFs Energy - IFs Energy resource endowments - IFs Fossil energy resources - IFs Uranium and other fissile resources - IFs Non-biomass renewables - IFs Energy conversion - IFs Electricity - IFs Heat - IFs Gaseous fuels - IFs Liquid fuels - IFs Solid fuels - IFs Grid, pipelines and other infrastructure - IFs Energy end-use - IFs Transport - IFs Residential and commercial sectors - IFs Industrial sector - IFs Other end-use - IFs Energy demand - IFs Technological change in energy - IFs Land-use - IFs Agriculture - IFs Emissions - IFs GHGs - IFs Pollutants and non-GHG forcing agents - IFs Carbon dioxide removal (CDR) options - IFs Climate - IFs References - IFs
Corresponding documentation
AIM-Hub BLUES C3IAM COFFEE-TEA DNE21+ GCAM GEM-E3 GRACE IFs IMACLIM IMAGE MESSAGE-GLOBIOM POLES PROMETHEUS REMIND-MAgPIE TIAM-UCL WITCH COFFEE-TEA
Previous versions
Archive of IFs version 7.36
Model information
Model link	https://pardee.du.edu/access-ifs
Institution	Frederick S. Pardee Center for International Futures, University of Denver (Pardee Center), Colorado, USA, https://pardee.du.edu/.
Solution concept
Solution method	Dynamic recursive with annual time steps through 2100.
Anticipation	Myopic

The dominant population equation is a simple addition of births (BIRTHS) at the bottom of the single-year cohort distribution, subtraction of deaths (DEATHS) from each population cohort, and advance of people to the next cohort over time. Although the output from the IFs interface displays population aggregated into standard 5-year age categories, the model maintains and uses single-year categories internally to be consistent with its one-year time steps, thereby avoiding numerical diffusion of aging via premature movement of people aging into any 5-year category (in the bottom cohort year) on up the next higher 5-year category in the following year.

Births are most immediately a function of the total fertility rate (TFR) and numbers of women in their child-bearing years. Over time TFR responds especially to educational attainment of the adult population, infant mortality rates, and contraception usage rates (some attention to differential fertility between urban and rural populations, which are represented in IFs and affect fertility rates around the world, would be a useful addition). The model user has direct control over TFR with a multiplier and, to avoid movement to unreasonably low rates in low fertility countries, with a parameter specifying long-term stabilization level for TFR. As is common in IFs, the TFR function, including control by a minimum TFR value and the possibility of increase to that minimum from below for countries (like Italy and South Korea) that may have base year values below a value specified by users, is not simply an equation, but an equation wrapped in algorithmic logic that attempts to prevent unrealistic behavior in the long run. Long-term modeling requires not only equations, but structural logic elaborated in algorithms.

Deaths are primarily a function of age-sex specific mortality rates computed within the IFs health model where they change over time with adult education, GDP per capita and technology change, as well as with selected mortality-cause-specific proximate drivers (e.g. indoor solid fuel-use and urban air pollution). The model user has direct control over all deaths with a general mortality multiplier or with an alternative, cause-specific mortality multiplier. The population model also computes morbidity. The principal data source for mortality and morbidity by cause, age, and sex is the Global Burden of Disease project.

The model further represents inward and outward migration rates and numbers, as well as foreign-born population totals.  Although the principal data source for initialization of all demographic data series are the newest releases by the United Nations Population Division, data on bilateral (or dyadic) migration flows also come from Guy Abel (2019).  Given migration-based population stocks abroad, the model also computes remittances, which in the economic model adjust household income in sending and receiving countries, as well as affecting current account balances.