Public debt/Addendum


 * ΔD = (D + F + Dr)/{Y(1 + r)} - D/Y

let 1/{Y(1 + g)} = A then:
 * = A(D + F + Dr) - D/Y
 * = A( D + F + Dr - D/AY)
 * = A( D + F + Dr - D - Dg)

substituting for A:
 * = {F + D(r - g)}/{Y(1 + g)}

or, approximately
 * = {F + D(r - g)}/Y