more limited action would not enable the objective to be achieved as effectively and rapidly. third, proportionality stricto sensu implies that the expected benefits of the ecb ’ s actions must outweigh their costs. these principles provide for a hierarchy of tools, where unconventional measures should be used only once conventional measures have been exhausted. let me address, then, the criticism that the distributional consequences of unconventional monetary policy undermine central bank independence. it is worth recalling that monetary policy always has distributional effects. cutting short - term interest rates tends to reduce the income of savers and boost the income of debtors and the wealth of asset holders. it also affects incomes through the macroeconomic effects on employment and wages. in short, not only does conventional monetary policy have distributional effects, it partly works through causing them. in normal times, these effects are viewed as being of secondary importance to the aggregate welfare benefits of price stability. in other words, they are proportionate. moreover, any distributional consequences of monetary policy action need to be set against the distributional consequences of inaction. sudden, unexpected deflation has distributional 2 / 5 bis central bankers'speeches consequences. ten million more people are now employed in the euro area than when unemployment peaked – this number would be much smaller had the ecb not acted, even though we only have a narrow mandate to maintain price stability that does not cover employment. the ecb also attempted to minimise unwanted side effects by carefully designing our tools. for example, it became clear that our asset purchase programme ( app ) was contributing to challenging conditions in the repo market. 8 by the end of 2016, around half of german government bonds were trading “ special ” – that is, at a premium to general collateral. we modified our securities lending programme, including by accepting cash as collateral, to mitigate the impact of the app on repo markets. today, the share of specials is generally below 10 %. in general, prevention is better than cure. that ’ s why we established many safeguards and restrictions, particularly in our public sector purchase programme, to avoid interfering with fiscal and economic policy and providing monetary financing to governments. the stringent eligibility criteria and issue and issuer limits are examples of self - imposed restrictions which have been vetted by the european court of justice. 9 independence and the prohibition of monetary financing prevent central banks from behaving as a fiscal substitute. we have also increased transparency and enhanced accountability measures – the necessary counterparts

, a., webb, s. and neyapti, b. ( 1992 ), “ measuring the independence of central banks and its effect on policy outcomes ”, the world bank economic review, vol. 6, no 3, pp. 353 – 398 ; and berger, h., de haan, j. and eijffinger, s. ( 2001 ), “ central bank independence : an update of theory and evidence ”, journal of economic surveys, vol. 15, no 1, pp. 3 - 40. 4 see, for example, tucker, p. ( 2018 ), “ pristine and parsimonious policy : can central banks ever get back to it and why they should try ”, in hartmann, p., huang, h. and schoenmaker, d. ( eds. ), the changing fortunes of central banking, cambridge university press. see also summers, l. ( 2017 ), “ central bank independence ”, bank of england : ‘ independence – 20 years on ’ conference. 5 there appear to be almost no limits to the ideas for new fields of activity to entrust to central banks, as our long list of opinions on the subject shows. see, for example, the ecb opinions mentioned in the ecb ’ s 2018 convergence report, pp. 30 – 32. 6 mersch, y. ( 2017 ), “ central bank independence revisited ”, keynote address at the symposium on building the financial system of the 21st century : an agenda for europe and the united states. 7 there is a wide range of empirical evidence demonstrating the effectiveness of unconventional measures 4 / 5 bis central bankers'speeches across a range of countries. see, for example : joyce, m., lasaosa, a., stevens, i. and tong, m. ( 2011 ), “ the financial market impact of quantitative easing in the united kingdom ”, international journal of central banking, vol. 7, no 3, pp. 113 – 161 ; wu j. and xia, f. ( 2016 ), “ measuring the macroeconomic impact of monetary policy at the zero lower bound ”, journal of money, credit and banking, vol. 48, no 2 - 3, pp. 253 – 291 ; and eser, f. and schwaab, b. ( 2016 ), “ evaluating the impact of unconventional monetary policy measures : empirical evidence from the ecb ’ s securities markets programme ”, journal of