Earlier this year, economist Thomas Piketty caused a stir with a book arguing that the future in advanced economies could see a relentless concentration of wealth among a small sliver of families, whose fortunes would increasingly dwarf those of the typical citizen. The last couple of weeks have seen the release of a couple of key barometers of wealth inequality in America, and combining them, it’s easy to see that this hypothesis of ever-concentrating wealth seems likely indeed. In the past month, the Federal Reserve released its triennial Survey of Consumer Finance (SCF) for 2013, while Forbes magazine released their annual list of the 400 wealthiest Americans.

The SFC is the most comprehensive and high-quality measure of Americans’ wealth up and down the distribution. It makes a special effort to sample very high wealth American households, but actually explicitly excludes listed members of the Forbes 400 (for reasons of confidentiality). The Forbes 400, as is well known, puts a dollar value on the net worth of the 400 wealthiest Americans. There is plenty of material in these releases to assess the current state of wealth inequality in America.

Take one example, that we’ve calculated before: comparing the family wealth of six of the wealthiest members of the Walton family (reported at just under $145 billion in 2013) with the number of American families that you could add together and still have their net worth come in less than the 6 Walton heirs: 52.5 million, or 42.9 percent of American families.

Some have objected to this statistic on the grounds that the negative net worth families (11.5 percent of all American families) somehow shouldn’t count in this calculation. So, try another statistic: how many families that held the median wealth would you need to add together to equal the holdings of the six Walton heirs: more than 1.7 million. The median wealthholder in the United States, remember, has more wealth than half of all American families and less wealth than half (around $81,200 in 2013).

So, what this statistic means is that you’d essentially need a large city’s worth of these typical American families to equal the wealth of the six Walton heirs. And this number has grown steadily over time, as the figure below shows. The falling wealth of the median family (driven largely by the housing bubble burst) and the steadily rising wealth at the very top—including the Walton heirs—have combined to make the gap between them larger and larger over time.