5 / 12  BIS central bankers' speeches  Duration of investment book and the maturity structure of G-Secs The high interest rate exposure of banks from their G-Sec portfolios is attributable to not only the size of their holdings, but also to the increasing maturity of primary issuance.
The weighted average maturity of the stock of Government securities has increased steadily from 9.66 yrs in 2012–13 to 10.67 yrs in 2017–18 (Chart 4). The average tenor of annual issuance during the last five years has been high at around 15 years. What are implications of this changing maturity structure of G-Secs for the duration of bank investment portfolios?