How do economists define labor force

How do economists define the labor force? And one more thing... A person is qualified as an employee by being 16 or more years old AND
-Having worked at least an hour and gain wages during the past week. OR
-Participate in a family business at least 15 hours, without salary given. OR
-Have jobs but inevitably have to take a break Employment Unemployment Economist define the labor force as people who are hired or searching for career.
Where is the infomation from? 100 years ago, agricultural 
workers dominated, presently, 
it is IT era. What about the next decade?

Ha4d wnr 7se less gsb4irl was sso cool gabriel