Much like Oregon and Washington have done, Maryland decided to "stick it to the wealthy" to make up budget shortfalls and increase funds received. As warned, the exact opposite happened. From a Wall Street Journal article;
"We reported in May that after passing a millionaire surtax nearly one-third of Maryland's millionaires had gone missing, thus contributing to a decline in state revenues. The politicians in Annapolis had said they'd collect $106 million by raising its income tax rate on millionaire households to 6.25% from 4.75%. In cities like Baltimore and Bethesda, which apply add-on income taxes, the top tax rate with the surcharge now reaches as high as 9.3%—fifth highest in the nation. Liberals said this was based on incomplete data and that rich Marylanders hadn't fled the state."
"Well, the state comptroller's office now has the final tax return data for 2008, the first year that the higher tax rates applied. The number of millionaire tax returns fell sharply to 5,529 from 7,898 in 2007, a 30% tumble. The taxes paid by rich filers fell by 22%, and instead of their payments increasing by $106 million, they fell by some $257 million."
And, Maryland's unemployment during this time?
Democrats will never learn.