The Madison Paper Industries mill is closing in May, putting more than 200 employees out of work and adding to the decline of Maine’s paper industry. Madison Paper will be the fifth Maine mill to shut down in a little over two years, and its closure will leave just six mills operating in the state. Although some mills continue to operate profitably, the domestic paper industry has been grappling with the declining demand and cheaper imports, leading in recent years to mill closures, bankruptcies and layoffs.