It's not difficult to see evidence of income disparity in San Francisco. The headquarters of Twitter, now valued at around $20 billion, looms massively over a neighborhood plagued by homelessness, drug addiction, and prostitution. Median rents continue to hit record highs, and despite the wealth that continues to pour into San Francisco thanks to the tech boom, the number of homeless individuals has remained more-or-less the same since 2005.

The gap between rich and poor is widening across the country, but according to a new study, San Francisco income inequality was found to be not only above the US national average -- it was even slightly worse than that of Rwanda, which is among the most unequal countries in the world.

Using the "Gini Coefficient," the same metric the World Bank uses to measure income inequality, the city's Human Services Agency gave San Francisco a score of 0.523 ("zero" is the lowest possible score, indicating that every citizen shares wealth equally, and "one" is the highest, which would mean that one person possesses all the wealth). If San Francisco was a country, it would rank as the 20th most unequal nation on Earth, according to the World Bank's measurements.

The United States performs a bit better, scoring a 0.45 but is far behind Denmark and Sweden which, with scores of 0.24 and 0.25, are the world's most egalitarian countries.

It's important to note that while many economists agree that income inequality hurts economic growth, it isn't a pure reflection of a country's prosperity or quality-of-life. Thanks to support received by federal and municipal social services and philanthropic organizations, being poor in San Francisco is not the same as being poor in Rwanda.

But the study shows that the class tensions embodied by Google Bus protests and calls for eviction reform, are based on something more than anecdotal evidence. And while tech firms bringing in a surge of high-paid workers aren't the only factor contributing to higher rents and income disparity, these and other companies at the top are reaping the benefits while many of the city's poorest residents remain in poverty.

[Photo by Dan Raile for Pando]