nan roman is the c.e.o. of the national alliance to end homelessness. and she joins me now. roman, thank you for joining us, and, full disclosure, i serve on the board of the alliance. but first, let me ask you, how serious is the homelessness problem in this country compared to a few years ago? >> well, the problem o homelessness has been getting worse in this country compared to a few years ago. from 2007 to 2016, it had been going down pretty steadily every year. starting in 2016, it has been creeping up every year, including this year, as far as we know. >> woodruff: and do you understand why that is? >> i think it is largely due to the lack of affordable housing and housing getting more expensive, and also what people earn, are purchasing less housing. >> woodruff: and is that due to federal policies, state policy? what would you ascribe it to? >> it's due the market, to some degree. i mean, we really don't have an adequate supply of housing in the u.s. anymore. about five million units short of having an adequate supply of housing overall. and in theffordable housing c