Happiness is in the eye of the beholder, but an annual global index of the happiest cities puts Minneapolis at the very top of its list in the United States.

Minnesota's largest city joins world-class counterparts such as Singapore and London in an index by the global Institute for Quality of Life, which ranks cities using various factors that contribute to the happiness of residents — or lack thereof. While tops in the U.S., Minneapolis doesn't appear on the list until the 18th spot.

The Happy City Index categorizes cities as gold, silver or bronze, based on 24 factors divided into five key categories that include citizens, governance, environment, economy and mobility.

What constitutes a city of happy people will differ for a child looking for a good playground, a corporate professional in search of an efficient commute or a senior citizen, the institute said.

"We never create one model of the happiest individual. Our work and experience have allowed us to gain confidence that the concept of a high quality of life is extremely subjective, conditioned by the history, tradition, religion or geopolitical location of the country in which a person lives," the institute said.

Areas under consideration in the determination of quality of life include education, social inclusion of residents, accessibility of public transport and availability of green areas and access to culture.

Cities are moving landscapes, the index said, meaning each year in a city comes with its own set of highs and lows. Information about public services is verified periodically and the ranking is released annually.

The European cities of Aarhus, Denmark; Zurich, Switzerland; and Berlin, Germany landed in the top three spots.

The U.S. cities of Boston, Baltimore and Washington also scored in the top 100.