From a paper on the economies of scale of living together (cohabitating):

Both partners in married couples require about 80% of total household income in order to be as well off when living alone. This percentage is much smaller for cohabitating couples, where the female partners only need about 52% and male partners about 63% of total household income.

I can tell you one of the most annoying things about being single is the cost of eating. It's wasteful to cook for yourself, unless you want to eat the same thing day in and day out (I don't like eating leftovers).

. . .

This site claims that the following data is from the Federal Reserve Board’s 2004 Survey of Consumer Finances but I could find no references to it in the actual data, so take it with a grain of salt:

Net Worth Statistics by Age

Age: 20-29
Median Net Worth: $7,900 
Top 25%: $36,000 
Top 10%: $119,300 

Age: 30-39
Median Net Worth: $44,200 
Top 25%: $128,100 
Top 10%: $317,800

Age: 40-49
Median Net Worth: $117,800 
Top 25%: $338,100 
Top 10%: $719,800 

Age: 50-59
Median Net Worth: $182,300 
Top 25%: $563,800 
Top 10%: $1,187,600 

Age: 60-69
Median Net Worth: $209,200 
Top 25%: $647,200 
Top 10%: $1,429,500