In general, an indicator is a measurable variable produced from any number of expressions of value. An indicator is used to represent an associated factor or quantity that is otherwise non-measured or non-measurable in the material sense such as number, volume or weight. For example, a consumer price index (CPI) serves as an indicator of general cost of living that consists of many factors combined, some of which may be qualitative—rather than quantitative—in nature and, therefore, are not included or computed to produce the CPI.

Indicators are common statistical devices employed in economics, development, project monitoring and evaluation, among other fields of endeavor. Three types of indicators are common: (1) structural, (2) process and (3) outcome indicators. The first reflects what conditions prevail before an intervention, while the second expresses the effort exerted and the progress toward the objective or goal during the intervention. The third type of indicator expresses the degree to which the desired result has been achieved.

In the context of development, the global 2030 Sustainable Development Agenda seeks positive change across 17 Sustainable Development Goals (SDGs), subdivided into 169 Targets. For each Target, UN Member states and Charter-based agencies are the main decision makers to determine the one or two globally accepted indicators to measure. So far, the total of SDG indicators totals 232.

In the case of SDG indicators, big-data approaches dominate the selection and eventual capture of data corresponding to each indicator. Such approaches seek potentially to assist traditional statistical methods in collecting and analyzing data to support the calculation of SDG achievement. They also aim to replace costly occasional surveys of traditional statistics with cheaper real-time information.

So far, the majority of SDG indicators identified and agreed upon are structural indicators, without their process and outcome complements. This complicates the eventual assessment of effort and measurement of change over the life of the global development policy (ending in 2030). While SDG indicator development remains underway, the indicators least developed at the time of this publication are those related to land administration and management. (See The Rush for Land Indicators in this issue.)