Sometimes, there are slight differences in the liquidity of otherwise equivalent securities. Treasury bonds, i.e., bonds issued by sovereign governments, are issued and sold on markets at regular time intervals in order to finance public spending and debt. The most recently issued bonds are called on-the-run, whereas their older relatives are called off-the-run. On-the-run bonds are more actively traded, and liquid, and this has an impact on their price. Some traders may try to take advantage of this price differential by suitable trading strategies, buying the cheaper bonds and short-selling the more expensive ones.