^ Let me find my numbers (admittedly, they date from the 2000 Census; I haven't had the time or inclination to update this information with block data for 2010).
Ahh, here we go:
Central Phoenix consists of roughly the 1960 city limits of Phoenix. It had about 760,000 people living in about 140 square miles in 2000, excluding some preserve lands, and had a density of well over 5,000 people per square mile (ppsm). By comparison, the rest of the city covers about 400 additional square miles, with about 550,000 people. Yes, that is an overall density of just over 1,000 ppsm, but a lot of this land is undeveloped or large desert preserves.
As a reference point, Phoenix had about 430,000 people in 1960. That same area in 2000 had about 760,000.
The per capita income of central Phoenix is about 10% less than the average for the entire city. If you removed Camelback East, which has a lot of money, from these numbers, the per capita income for central Phoenix would be almost 30% below the average.
A discussion about population density:
Most U.S. cities follow the following paradigm: Very high population densities in the core (peak), followed by steep drops in densities as you move into the suburbs. If you graphed this out, it would look like a very steep mountain. For example, Kansas City still has some inner city neighborhoods with 10,000 people per square mile or more. Note during the 1940s, these same inner city areas were over 20,000 ppsm. The Kansas City suburbs, by contrast, are very low density, with many houses on acre lots or more, yielding densities of about 2,000 to 1,000 ppsm or less. Phoenix never had that sort of density in the core, so here, the "inner city" looks like a large plateau with densities of about 5,000 ppsm. This drops very gradually into the built Phoenix suburbs, with many reaching densities of 3,000 to 4,000 ppsm or more.
Put another way, older U.S. cities are at least twice as dense in the core, and half as dense in the suburbs or less. This is why the "urban footprint" (or urbanized area, if you will) of Phoenix is far smaller than eastern/northern cities. For one thing, land costs are much higher in Phoenix, ensuring smaller lot sizes.
Overall, my prediction for the 2010 census will probably show similar numbers. There might be a slight drop from the 760,000 counted in central Phoenix in 2000, offset by a sizable increase in the farther flung reaches of the city. It is fairly clear from glancing over the preliminary block data that central Phoenix may have lost as many as 100,000 Hispanics from 2006-on, and may have continued to have white flight (which has been happening in certain inner city neighborhoods of Phoenix since World War II, just like in many other U.S. cities).
--don