New reporting rules have severely delayed corporate filings.

Saudi Arabia’s 14 exchange-listed petrochemical firms only completed their Q1 financial filings on 11 May, some three weeks behind previous years’ schedule.

They notched up their best quarterly returns since Q2 2015 with earnings in recent years not surprisingly closely tracking movements in oil prices (see chart) The companies typically buy feedstock at low fixed Saudi prices but sell their output at oil-linked...