It is very difficult to determine how many homeless people there are in the world because countries have different legal definitions for homelessness. Natural disasters and sudden civil unrest also complicate the picture. The best we have is a conservative estimate from the United Nations in 2005, which puts the number of homeless at 100 million.
The 2005 U.N. report looked only at people who did not have any homes whatsoever. Not included were people who lived in terrible semi-permanent places such as abandoned buildings, vehicles, hastily put together shelters or tents. The report also did not include the "hidden homeless," who bounce from shelter to shelter or from friend's house to friend's house. Countries such as England include the hidden homeless as legally homeless.
There has not been a fully comprehensive count of the numbers of homeless since the U.N. report in 2005. No one really knows just how many people do not have any permanent place to call their own. It is estimated that there could be as many as another 100 million hidden homeless in the world, bringing the conservative estimate of the total population of homeless to 200 million.
This count does not include cultures that live like nomads, including Romany gypsies in Europe and some remaining groups of Mongolians who follow their herds. These peoples are rapidly diminishing because of the lure of modern conveniences and a lack of places to camp or graze their herds.
There does not seem to be an international consensus on what makes a person homeless. In some countries' eyes, there are only 100 million homeless in the world. In others, such as England's, there are closer to 200 million. Because there's no agreement on what makes a person homeless, it's hard to know just how big the problem is.
The solution to homelessness is complex. It's not enough to just give donations to homeless shelters. There must be jobs that pay living wages for homeless people, so they will not go right back on the streets again if they should get sick and miss work or get laid off. The National Coalition for the Homeless claims that 13% of American homeless have full-time jobs but still cannot afford housing. A 2008 Seattle study showed that homeless people who were given housing first were able to get off drugs and get a more or less normal life. Over time, society paid less to house the homeless first than to wait for them to nearly die on the streets and then get emergency housing.