Most states are gaining population. Only a few are not. Vermont is one of them. An analysis of U.S. Census data from 2010 to 2015 shows that while North Dakota, Texas, Colorado and Utah grew by more than 8 percent (the top four in that order) West Virginia (50 out of 50), Vermont (49 out of 50) and Maine (48 out of 50) grew by less than one tenth of one percent.
A slightly different analysis of population trends presented in an article entitled “The Fastest Growing and Shrinking States” by Michael Sauter, Evan Comen and Samuel Stebbins on the website 247wallst.com in January 22, 1016 listed West Virginia as the fastest shrinking state followed by Illinois and Vermont. Vermont lost 0.12 percent.
http://247wallst.com/special-report/2016/01/22/the-fastest-growing-and-shrinking-states/5/
Population growth (or decline) is a combination of births, deaths and net migration into or out of the state.
An article entitled “The States with Declining Populations” by Mike Maciag in January 19, 2016 concluded that not only is Vermont full of old people, but the birth rate among young people is low, so as old people die they are not replaced. Furthermore, many young Vermonters leave the state to find better jobs. At the same time, Vermont has not had much net foreign immigration as in cities like New York.
http://www.governing.com/topics/mgmt/gov-states-losing-population-census.html
None of this is new. Since at least the 1850s young women left the farms and headed to the factories of New Hampshire and Massachusetts. Likewise, young men headed off to the Civil War never to return once they saw how productive the farms of other areas were compared to rock-laden, northern New England. Northern New Englanders have a long history of going elsewhere for opportunity.
it is also why the population of Vermont in 1960 was not all that much larger than it was in 1860, a century earlier.