Many people see a homeless person on the streets, and they think that such a situation could never happen to them. Recently, PBS chronicled vital statistics databases and homeless shelters all across the U.S. to determine the biggest causes of homelessness.

Lack of adequate health care is right at the top of the list. 1/3 of Americans have no health insurance, and most of these are low-income workers. The sicker they become, the more likely they are to be laid off. Without health care, they cannot get better. If they cannot get better, they cannot work. As a result, they end up homeless and the vicious cycle continues.

Domestic violence is another major factor of homelessness, especially in women. This goes hand in hand with mental illness, which can spur domestic violence and victim abuse. Since many hospitals were closed in the 1980s to de-institutionalize the mental health industry, patients have become homeless.

Finally, substance abuse is another major cause of homelessness. Even Hollywood actors have fallen into homelessness when they fall to addiction. No one is immune to harmful substances, no matter how much money or fame they have.

For a long time there was great debate over how to accurately describe homelessness and its pervasiveness into American culture. There are two well recognized ways to describe homeless numbers:

• Point in time: measuring the number of homeless people at any one given time. A “snapshot” of homeless numbers. “Critics say this method is likely to overestimate the number of chronically homeless and underestimate the number of people who experience temporary homelessness.”

• Period prevalence: recording homeless numbers over a set period of time. “Critics of this method point to the difficulty of standardizing measurements. Other affecting factors in measuring homeless rates include the duration of counting and time of year of counting.”

HUD has adopted a modified point-in-time method that measures homeless numbers in shelters and homeless numbers on the streets. After a thorough examination of numbers in 2005, HUD came up with a baseline of over 744,000 homeless people at any given time. This baseline number helps establish a measurement for future homelessness. Today, in 2009, we can look at the numbers and determine whether or not we have more homeless people or less than 2005.

For more information see HUD and PBS