##b. we developed our own composite uncertainty indicator which combines four components : systemic stress, uncertainty of private households and firms, political uncertainty and financial risk aversion. measurement difficulties were also an issue professor bloom had to tackle in the second strand of his research, namely in his research on the role of management practices in driving productivity and growth differentials across companies and across countries. due to an absence of good quality data on management practices, little prior research was conducted on this important topic. to address this gap in the literature, nicholas bloom, together with john van reenen of the london school of economics, developed a methodology for quantifying management practices. they carried out a large research project which used a new survey approach to measure management practices in a systematic way in more than 4, 000 manufacturing firms across europe, the us and asia. the aspects of management practices their approach focuses on are systematic performance monitoring, setting appropriate targets, and providing incentives for good performance. they showed that firms with better management practices are larger, more productive, grow faster, and have higher survival rates. a conservative estimate indicates that differences in management practices see nicholas bloom, 2011, “ the uncertainty shock from the debt disaster will cause a double - dip recession ”, voxeu. org, 22 august ; and scott baker, nicholas bloom and steven j. davis, 2012, “ the rocky balboa recovery ”, voxeu. org, 20 june. there is a vast body of literature that builds on nicholas bloom ’ s uncertainty research. i will only name a few papers which involved ecb researchers. using german data, popescu and smets find that uncertainty shocks are less important drivers of business cycles compared to financial risk aversion shocks ; see adina popescu and frank smets, 2009, “ uncertainty, risk - taking and the business cycle in germany ”, cesifo economic studies 56 ( 4 ), 596 – 626. bekaert et al. document that a lax monetary policy in the us decreases both risk aversion and uncertainty, with the former effect being stronger ; see geert bekaert, marie hoerova and marco lo duca, 2013, “ risk, uncertainty and monetary policy ”, journal of monetary economics, 60 ( 7 ). see helene rey, 2013, “ dilemma not trilemma : the global financial cycle and monetary policy independence ”, paper presented at the jackson hole economic policy symposium. incidentally, helene rey was the 2006 german

. 1341 – 1408 ; and nicholas bloom and john van reenen, 2010, “ why do management practices differ across firms and countries? ” journal of economic perspectives, 24 ( 1 ), pp. 203 – 224. in a recent contribution, nicholas bloom and co - authors showed that us multinationals obtained higher productivity from it than non - us multinationals and that establishments taken over by us multinationals ( but not by non - us multinationals ) increased the productivity of their it. they attributed a bulk of productivity differences to differing people management practices across us and non - us firms. see nicholas bloom, raffaella sadun and john van reenen, 2012, “ americans do i. t. better : us multinationals and the productivity miracle ”. american economic review 102 ( 1 ), pp. 167 – 201. for more information about the network visit http : / / www. ecb. europa. eu / home / html / researcher _ compnet. en. html. bis central bankers ’ speeches