Legal Definitions - ex post

Ex post is a Latin term meaning "from after" or "after the fact." It refers to an analysis, evaluation, or judgment made after an event has already occurred and its outcomes are known. When something is considered "ex post," it means looking back with the benefit of hindsight, using all available information about what actually happened.

Here are some examples to illustrate the concept of ex post:

• Imagine a city council implementing a new traffic light system at a busy intersection. An ex post analysis would involve collecting data on traffic flow, accident rates, and pedestrian safety after the new system has been in operation for several months or years. The council would then evaluate whether the new lights actually improved safety and reduced congestion based on these real-world results.

  This illustrates ex post because the evaluation is conducted after the system is in place and its effects can be observed and measured.

• Consider a company that launched a major marketing campaign for a new product. An ex post assessment would involve reviewing the actual sales figures, customer feedback, and market share changes after the campaign has concluded. The company would then determine the campaign's true effectiveness based on these concrete outcomes, rather than on initial projections or expectations.

  This demonstrates ex post because the success of the marketing campaign is judged by looking back at the actual performance data once the campaign has run its course.