The U.S. budget deficit will decline slightly to $468 billion (310 billion pounds) this fiscal year, the lowest level since President Barack Obama took office, congressional forecasters said on Monday in a report heralding the end of a brief period of dramatically shrinking red ink. The deficit, down from the $1 trillion-plus levels of Obama’s first four years and a $483 billion gap in fiscal 2014, will stay largely flat in 2016, then begin to march upward due to rising costs for debt and caring for fast-retiring Baby Boomers.