"Amazon's corporate income tax bill is so small, though, because its corporate income (aka profit) is so small. Wal-Mart's pretax income since 2008 has totaled $209 billion, Amazon's less than $11 billion. So while Amazon's rise to fifth-biggest market cap in the world on the strength of such small earnings is a fascinating and perhaps disturbing phenomenon, it doesn't necessarily signal a problem with our system of corporate taxation."