The deficit is accrued every year and new deficit is added to past yearly deficits. Sum all the deficits together and you get the national debt as the total owed by taxpayers. If Obama cut the deficit by 2/3's that's great. What year(s) did he do that? At the end of his eight years of presidency his total deficits still added up to nearly 10 trillion dollars. Add that to the prior national debt already on the books and we have a grand total of 19 trillion dollars. Don't get me wrong, Trump is continuing government deficit spending which now has crossed 20 trillion dollars. At some point we default just like you or me telling the bank we can't carry anymore credit card debt. Boom! We file bankruptcy.