They always undercount people. They only count people who recently had a job who are still trying to find a job.
They don't count people who
1. never had a job
2. gave up
3. got a part time job at McDonalds to replace their $100k a year job.
GDP per capita roughly accounts for those factors: if you never had a job or stopped looking for one, then you count towards capitation, but not GDP; if you make less money than you used to, then you contribute less to GDP.
Not when the rich are growing richer much faster than anyone else. If you ignore that, you'd still have to take into account both inflation and labor pool growth.
