Much of the recent discussion about the fiscal cliff has focused on the role of the wealthy and their obligation to shoulder the public debt load. With the debt at $16T and the relative concentration of wealth in the US, the wealthy might not ultimately have much of a choice. The top quintile of wealth is going to have to shoulder almost all of the load.
America is a wealthy country, so technically there is enough money to extinguish the whole debt if we needed to, but it would likely take extending the scope of taxation beyond income and into wealth. The savings rate in the US ("leftover" income) is already very low, so there isn't a whole lot of room to tax income more without severely impacting consumption. There is, however, plenty of wealth, but it happens to be highly concentrated because low income households don't save much. The top 20% of households hold 85% of the country's net savings.
Below is a chart of what the richest Americans' wealth looks like in relation to the Federal debt. The Forbes 400 could only cover ~10% of the total. The top 1% could cover the whole amount, but it would require a one time tax of 71% of their net worth (which includes assets like real estate, which would be tricky to implement).
If Uncle Sam wanted to keep a hypothetical debt extinguishment tax to 30% of an individual household's net worth, it would have to extend the tax across the top 20% of households, which would include households with an average net worth of ~$700k (that works out to ~210k for that household).
|Source: Federal Reserve, Avondale Estimates of Net Worth Based on 2007 Wealth Concentration Statistics.|
Importantly this analysis only includes today's debt. It does not take into account the unfunded liabilities from social security and medicare. It's a little scary to think that the majority of American households have almost no savings and will be absolutely dependent on these programs as elderly. These two programs combined are estimated to have an NPV liability of ~$50T, which theoretically wipes out the net worth of the whole top 20%. Before anyone goes into crisis mode though, all that really means is that something will have to change over time.