If the national debt is upwards of 15 trillion and the government wants to decrease spending then why do they not reduce it over the next 40 years,afterall it did not happen over night?and this is how long a house mortgage is in most states.

Because that would double the debt-to-GDP ratios and compound them all the way up to 600% over that period.A GAO simulation of this scenario shows that Social Security. MediCare and MedicAid expenditures would exceed over 20% of GDP by themselves which is historically the ratio of taxes collected by the fed.Gradual reduction would lead to these mandatory programs taking up all the government revenues under this simulation.