I prefer to not add meaning to words which doesn't convey an objective, universal truth. In nature, the adult phase of an animal's life begins when it's capable of reproduction. In accordance with contemporary values, our society considers this phase beginning at a later age, usually around 18. If financial autonomy is the milestone people use to separate children from adults then a large portion of adults would fail to meet that criteria, including the majority of the lower class. The government has essentially become a surrogate parent that gives people an allowance via social programs. I'm always amused when someone lectures another person about being an adult when they themselves receive subsidized housing and/or thousands of dollars in welfare and food stamps. People with mental illnesses also have an additional barrier to overcome. When old age takes its toll, the elderly often rely on their children to take care of them, but they don't suddenly lose their adulthood when this happens. The word 'maturity' can have a subjective element to it. If we measure a person's maturity level by external factors according to what they have achieved in life, then someone like Adolf Hitler who rose to power and created his own empire, would be considered remarkably mature; though examination of his psyche suggests that he was quite emotionally immature. Kanye West is wealthier than most Americans, but the suggestion that he's a mature adult because of his success is downright laughable. He is, however, an adult - as is anyone who is sexually mature (or according to the law, 18 years of age).
