[shagie]

A dollar in an account is fungible. Are all the dollars that show up on the W2 going to the same account? Do some of them not even hit the main account?

If I made $3000 this month and $300 of that went to a retirement account and $1000 of that went to tax withholdings and another $300 went to child support, and of the remaining $1400, I had direct deposit put $1000 in savings and $400 in allowance... how would that be represented?

I contend that for this (these numbers are purely made up for ease of talking about):

    (income 1)
    $3000 -> $300 child support
          -> $300 company retirement plan
          -> $1000 tax withholdings 
          -> $300 allowance -> {various 'fun' expenses}
          -> $1100 savings  -> {various 'not fun' expenses}

    (income 2)
    $2000 -> $700 tax withholdings
          -> $200 allowance -> {various 'fun' expenses}
          -> $1100 savings  -> {various 'not fun' expenses}

The 'allowance' and 'savings' are each one bucket that have a net $500 and $2200 coming in to them respectively.

Having $2000 and $3000 go into one big bucket of a 'main' account, while working under the 'all money is fungible' fails to capture some reality of how money flows. For example, if income 1 loses their job, child support goes to $0 (not $300 from income 2) as does the $300 for retirement and the $1000 for tax withholdings.