"Wealth" has come to mean an abundance of items of economic value, or the state of controlling or possessing such items, and encompasses money, real estate and personal property. In many countries wealth is also measured by reference to access to essential services such as health care, or the possession of crops and livestock. An individual who is wealthy, affluent, or rich is someone who has accumulated substantial wealth relative to others in their society or reference group. In economics, wealth refers to the value of assets owned minus the value of liabilities owed at a point in time.