The former head of the state-owned oil firm has presented stunning claims of high-level graft. Are they credible, and will the president pursue them? Museum curators usually try to add to their collections, but a new generation steeped in the restitution debate is doing just the opposite. And a data-led analysis of the suggestion that Twitter suppresses conservative views. For full access to print, digital and audio editions of The Economist, subscribe here www.economist.com/intelligenceoffer