For each country, survey and census data are plotted on a timescale from 1980 to the present. A linear trend line, based on the least-squares method, is drawn through these data points to provide estimates for all years between 1990 and 2012 (wherever possible). The total estimates are population weighted average of the urban and rural numbers.
Sanitation trend analyses at country level are made for improved sanitation facilities and open defecation. The estimates for improved sanitation facilities presented are discounted by the proportion of the population that shared an improved type of sanitation facility. The ratio (proportion of the population that shares an improved sanitation facility between two or more households, including those using a public toilet) derived from average of all available ratios from household surveys and censuses is subsequently subtracted from the trend estimates of improved sanitation facilities, and this gives the estimates for shared sanitation facilities.
With MDG target year in the horizon, in its latest estimates, the JMP made preliminary assessments of progress towards the MDG target, applying global targets to countries and regions. Method of assessment is based on 2012 coverage of improved water or improved sanitation:
- If the above is greater than or equal to 2015 target or 2012 coverage is greater than or equal to 99.5%: Met target;
- If the above is within 3% of the 2012 required target value: On track;
- If the above is within 3-7% of the required target: Progress insufficient;
- If the above is outside of 7% of the required target value: Not on track