Global economic activity is weak by historical standards with a slowdown in productivity the main cause, International Monetary Fund head Kristalina Georgieva said in Washington on Thursday, describing this as a “sobering reality.” Listing the main difficulties facing the global economy, Georgieva said: “Inflation is not fully defeated. Fiscal buffers have been depleted. And debt is up, posing a major challenge to public finances in many countries.” She put global growth at a little above 3% and noted concerns, including geopolitical tensions that were increasing the risks of economic fragment…