Drilling into the numbers: ExxonMobil

America’s biggest oil firm has long been recalcitrant on climate matters, so its new net-zero targets may seem surprising. We examine the substance of its pledges—and motivations. For an economist, tipping is an odd practice; whether you love it or hate it may be a question of control. And how unusual Novak Djokovic’s refusenik vaccine stance is among elite athletes. Additional audio courtesy of Tennis Australia. For full access to print, digital and audio editions of The Economist, subscribe here www.economist.com/intelligenceoffer