An overhaul of listing and trading rules has driven a 16-year-old board for start-ups on the Shenzhen Stock Exchange to an all-time high, and traders believe the listed companies’ above-average earnings growth and exposure to renewable energy will extend the record-setting run. The ChiNext 50 Index of the board’s 50 biggest stocks and the ChiNext Composite Index both broke highs set in 2015 this week, outpacing other equity gauges of yuan-denominated stocks, which have yet to fully recoup their...