I have posted links on income distribution by age. It varies by state but the income for being in the top 5 or 10 percent doesn't vary that much by state but at lower points it does. How much is enough? Depending on income level you might be surprised how much is needed to obtain lifestyle security down the road.
http://www.shnugi.com/income-percent...&income=150000
150k just gets you in the top 10 percent at ages 70-75.
The link is calculated for the above example.