Banks’ credit trading desks are reaping the rewards of a surge in portfolio and algorithmic trading activity, the latest sign of how technology is revolutionising the way corporate bond markets are traded to the benefit of a handful of mainly US banks. Portfolio trades in US corporate bond markets increased by nearly 50% last year to US$321bn, according to estimates from Tradeweb, as a growing number of investors are buying and selling large blocks of bonds in one go. The growth forms part of a broader shift towards electronic trading of corporate debt – a corner of finance that has been slower to adopt the kind of automated trading practices common in equity and currency markets.