Why Codan, CommBank, Rio Tinto, & Starpharma shares are sinking

In afternoon trade, the S&P/ASX 200 Index (ASX: XJO) is on course to start the week with a disappointing decline. At the time of writing, the benchmark index is down 1.8% to 7,233.7 points.

Four ASX shares that have fallen more than most today are listed…