# International Futures Help System

## Water and Sanitation

Forecasts of mortality related to diarrheal disease (all ages) depend on access to safe water and improved sanitation.  The regression models for each were estimated using the most recent year of data.

Full model formulations:

Distal Driver formulation:

INCOMELT1CS/POP*100 is the percentage of people living with less than \$1.25 per day

is health expenditures as a percentage of GDP

POPRURAL is the percentage of the total population living in rural areas

We use a logit formulation to manage the saturation of the 3 levels of access to either of these 2 services, so that the sum of the 3 levels never goes above 100 percent. In this logit formulation we compute the percentages using the regressions presented, then compute the final results following this method:

Where UnimpSWat% is the percentage of people with access to unimproved safe water, OthImpSWat% is the percentage of people with other improved access to safe water and PipedSWat% is the percentage of people with access to piped safe water. The same method is applied for estimating access to improved sanitation.

In order to compute the appropriate PAFs, IFs calculates the proportion of the population that falls into each of the following five categories:

• Category II: minimum of (share of population with piped connection for water supply, share of population with improved connection for sanitation)
• Category IV: minimum of (share with other improved or piped water supply not in category Vb or II, share with basic or improved sanitation not in category Va or II)
• Category Va: minimum of (share with basic or improved sanitation, remainder of those without other improved or piped connection for water supply that are not already in category VI)
• Category Vb: minimum of (share with other improved or piped water supply, remainder of those without shared or improved access for sanitation that are not already in category VI)
• Category VI: minimum of (share without other improved or piped connection for water supply, share without shared or improved connection for sanitation)

Each category has a different Relative Risk associated with it:

• Category II: 2.5
• Category IV: 6.9
• Category Va: 6.9
• Category Vb: 8.7
• Category VI: 11

The theoretical minimum or international reference is assumed to be 1, and thus the PAF equation gets simplified to:

[1] For more detail on this formulation please refer to Rothman, Dale. 2009 (Feb). “Formulae for Predicting Shares 23 Feb 2009.doc”, unpublished internal Pardee Center working note.