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 2015 (wherever possible; if 1990 baseline is not available 1995 estimate is used as a baseline). 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 with other households 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.
Drinking water trend estimates at the country level are made for piped water on premises, total improved as well as direct use of water from surface water sources.
With the current report, as the final report for the MDG period, JMP, assessed global progress towards the target, as well as applied the MDG target to the MDG regions and countries to assessed their progress towards the equivalent of MDG target for them. The method used are the following:
- For global and regional assessment: if the 2015 estimate is greater than or equal to target value, it is assessed 'Met target', otherwise 'Not met target'.
- For countries, the assessment is done slightly differently:
- If the 2015 estimate is within 1% pt of the target value, country/area or territory is assessed: Met target;
- If greater than two thirds progress towards the target achieved: Good progress;
- If the progress achieved has been between a third and two thirds required: Moderate progress ;
- If the progress towards the target has been less than the third required: Limited or no progress