section_path: Society and culture
section_name: Society and culture
paragraph_text: Society and culture
  
  Different cultures express age in different ways. The age of an adult human is commonly measured in whole years since the day of birth. (The most notable exception — East Asian age reckoning — is becoming less common, particularly in official contexts.) Arbitrary divisions set to mark periods of life may include juvenile (from infancy through childhood, preadolescence, and adolescence), early adulthood, middle adulthood, and late adulthood. Informal terms include " tweens ", "teenagers", "twentysomething", "thirtysomething", etc. as well as "denarian", "vicenarian", "tricenarian", "quadragenarian", etc.
  
  Most legal systems define a specific age for when an individual is allowed or obliged to do particular activities. These age specifications include voting age, drinking age, age of consent, age of majority, age of criminal responsibility, marriageable age, age of candidacy, and mandatory retirement age. Admission to a movie, for instance, may depend on age according to a motion picture rating system. A bus fare might be discounted for the young or old. Each nation, government, and non-governmental organization has different ways of classifying age. In other words, chronological ageing may be distinguished from "social ageing" (cultural age-expectations of how people should act as they grow older) and "biological ageing" (an organism's physical state as it ages).
  
  Ageism cost the United States $63 billion in one year according to a Yale School of Public Health study. In a UNFPA report about ageing in the 21st century, it highlighted the need to "Develop a new rights-based culture of ageing and a change of mindset and societal attitudes towards ageing and older persons, from welfare recipients to active, contributing members of society". UNFPA said that this "requires, among others, working towards the development of international human rights instruments and their translation into national laws and regulations and affirmative measures that challenge age discrimination and recognise older people as autonomous subjects". Older people's music participation contributes to the maintenance of interpersonal relationships and promoting successful ageing. At the same time, older persons can make contributions to society including caregiving and volunteering. For example, "A study of Bolivian migrants who moved to Spain found that 69% left their children at home, usually with grandparents. In rural China, grandparents care for 38% of children aged under five whose parents have gone to work in cities."