Notes about How the Calculations and Assumptions were set
The numbers are based off of the results of the 2013 Consumer Expenditure Survey by the Bureau of Labor Statistics. If you want to do your own analysis check out the raw data here: http://www.bls.gov/cex/home.htm. The number of samples per age vary quite a bit, so you might get unusual results for certain ages. Most of the numbers used in this tool are using the weighted average values. This is a little different than some of the other tools on the site that are using medians.
The effective tax rates listed are net of any refunds, tax credits, or similar subsidies that you receive after completing your annual taxes. So basically the calculation is [Federal Income Tax + Social Security + Medicare + State Income Tax + Local Income Tax ] - [ Federal Income Tax Refunds + State Income Tax Refunds + Local Income Tax Refunds]. The rate listed is the average calculated effective tax rate of American's surveyed in the Consumer Expenditure Survey who have a similar pre-tax monthly income (+/-20%). Due to the number and combination of income tax rates, deductions and exemptions that all households qualify for, this effective tax rate that is listed is probably not too close. To correct for this, I would recommend looking at your 2013 tax returns to find a more appropriate value.
The Peer Group Spending graphs are calculated in a similar way, where the spending of households with similar pre-tax monthly incomes are aggregated together to find a weighted average of their spending in that particular category. These numbers are for all Americans. So if you are wanting a more local view of this, you could go to a cost of living calculator to make your own adjustments for local market situations.
The budgets that are pre-loaded when you set a pre-tax income level are based off of an average American household earning $60,000 a year. The numbers start to get a little out of whack the higher in income you go. I decided to load the numbers, mostly to help you make a basic budget to give you a starting point instead of a blank slate.
If you start to generate budgets for incomes less than $51,000 per year, you may notice that their cash savings numbers are negative. This means that in the surveys for lower income people, they have been reporting that they are spending more per month than they are earning. This is a known oddity in the CEX survey, and here is an excerpt of their explanation: "However, there are reasons why expenditures exceed income for the lower income groups despite the use of imputed income data. Consumer units whose members experience a spell of unemployment may draw on their savings to maintain their expenditures. Self-employed consumers may experience business losses that result in low or even negative incomes, but are able to maintain their expenditures by borrowing or relying on savings. Students may get by on loans while they are in school, and retirees may rely on savings and investments. Read More"