The model Pressure-State-Answer is an economic model developed by OECD to represent the pressures exerted by the human activity on the environment, the state of the environment which results from it, and the answers of the Entreprise S.

Model PER comprises a series of environmental Indicateurs, which can be one of the three types:

• Pressure,
• State,
• Answer.

Various existing models

In the Anglo-Saxon world, the concept which corresponds to that of pressure is the driving force (or driving force), which is supposed to also adapt to the economic aspects, social, and institutional.

There exist several models:

• Pressure State Answer of OECD
• UNSD (the United Nations)
• Driving force-state-response of the Commission one Sustainable Development of the United Nations (CSD),
• Topic-indicator of the Commission one Sustainable Development,
• Driving force-press-state-impact-response (Eurostat and EEA)

See: environmental statistics on the site of the statistics of UNO