29 The relationship between public debt and nominal interest rates, nominal growth rate is expressed by the following formula.

*b*_{t} = *d*_{t} + *b*_{t-1}[(l + *r*)/(l + *g*)]

where,

*b*_{t} : current term debt outstanding (relative to nominal GDP)

*b*_{t-1}: preceding term debt outstanding (relative to nominal GDP)

*d*_{t} : current term primary deficit (relative to nominal GDP)

*r* : nominal interest rates

*g* : nominal GDP growth rates

The formula indicates that when nominal interest rates and nominal GDP growth rates are equal (r = g) and primary balance is achieved (d_{t} = 0), the current term debt outstanding is equal to the preceding term debt outstanding (b_{t} = b_{t-1}).