BD = Budget Deficit
PBD = Primary Budget Deficit
iD = Debt Service Payments
G = Government spending
TR = Tax Revenue
TP = Transfer Payments
T = Net Tax Revenue
BD = PBD + iD
PBD = G - T
PBD = G - (TR - TP)
PBD = G - TR + TP
BD = G - TR + TP + iD