Streetlight Effect (Drunkard's Search)

The observational bias of searching for something only where looking is easiest, not where the thing is most likely to be—named after the joke of a drunk looking for keys under a streetlight because 'the light is better here.' In research: studying phenomena that are easy to measure rather than phenomena that matter. In business: analyzing data that's available rather than data that's relevant. In strategy: focusing on markets you understand rather than markets with the best opportunities. The streetlight effect produces a systematic mismatch between where we look and where answers actually are.

When to use it

When analysis is constrained to available data rather than relevant data; when search efforts are concentrated in familiar areas; when easy measurement is substituting for important measurement; when 'looking where the light is' might be producing systematically wrong conclusions.

How it can help

For any search or analysis: ask 'am I looking here because this is where the answer is, or because this is where looking is easy?' In data analysis: the most important variables may not be in your existing dataset—don't limit your analysis to available data when the question demands unavailable data. In strategic planning: the best opportunities may be in unfamiliar markets—don't limit your search to familiar territory. In hiring: the best candidates may not be in your usual talent pool. The discipline: define what you're looking for FIRST, then find where to look—not the reverse.