What wealth (measured in $) is required to belong to 
1) top 5% of population of United States?
2) top 15% of population of United States? 
2) top 15% of the world?
Wealth can be either by an individual or by family.

Same question for income levels instead of wealth.

Answer must include reference data.

Check this:

"Percent Distribution of Household Net Worth, by Amount of Net Worth
and Selected Characteristics:  2000"
Get it from the US Census Bureau at
http://www.census.gov/hhes/www/wealth/1998_2000/wlth00-4.html

and for Income:

Income Distribution to $250,000 or More for Households:  2002
Get it at http://ferret.bls.census.gov/macro/032003/hhinc/new06_000.htm

I hope this will help

Yomgui

Hello
Your question has been unanswered for several weeks.
You may wish to consider reposting it as two, four or six different questions.
Also, while the US data may be fairly easy to obtain, you may want to
raise the price for the world data to make it worth a Researcher's
time.