b. ( 2016 ), “ assessing the implications of negative interest rates ”, speech at the yale financial crisis forum, yale school of management, new haven, 28 july ; and brunnermeier, m. and y. koby ( 2018 ), “ the reversal interest rate ”, princeton university, mimeo. 18 in this sense, considerations related to the introduction of universal reserves are also linked to the parallel discussion on the future size of central bank balance sheets, where some academics argue that central banks should keep balance sheets close to current levels in an effort to promote financial stability by providing a safe asset ( see, for example, greenwood, r., s. g. hanson and j. c. stein ( 2016 ), “ the federal reserve ’ s balance sheet as a financial - stability tool ”, paper prepared for the 2016 economic policy symposium proceedings, jackson hole : federal reserve bank of kansas city ). 19 for an illustration of this risk in relation to the swiss “ vollgeld ” initiative, see jordan, t. ( 2018 ), “ why sovereign money would hurt switzerland ”, speech at the swiss institute of banking and finance at the university of st. gallen, zurich, 3 may. 20 see, for example, ecb ( 2017 ), “ report on financial structures ”, october. 21 see cœure, b. ( 2017 ), “ the known unknowns of financial regulation ”, panel contribution at the conference on rethinking macroeconomic policy iv, washington d. c., 12 october. 22 see financial stability board ( 2017 ), “ assessment of shadow banking activities : risks and the adequacy of post - crisis policy tools to address financial stability concerns ”, july. 23 this includes a more thorough discussion on the design features of universal reserves that could potentially help mitigate a destabilising shift away from bank deposits. 24 interbank rates can also be steered towards the main refinancing rate in an environment of excess reserves. but this requires additional liquidity - absorbing operations. 25 moreover, investors are limited in what they can invest with banks due to their own risk control frameworks. 26 see also cœure, b. ( 2017 ), “ bond scarcity and the ecb ’ s asset purchase programme ”, speech at the club de gestion financiere d ’ associes en finance, paris, 3 april ; and cœure, b. ( 2017 )

13 march. the bis report also discusses a second option of introducing a central bank digital currency, namely in the form of restrictedaccess digital settlement tokens for wholesale payment and settlement transactions. 8 in reality, current private crypto assets only allow for pseudo - anonymity, as all transactions are publicly recorded. but users do not necessarily have to reveal their true identities. 9 see committee on payments and market infrastructures ( 2018 ), “ cross - border retail payments ”, bank for international settlements, 16 february. 10 see committee on payments and market infrastructures and markets committee, op. cit. joint research by the ecb and the bank of japan has found that distributed ledger technologies are not ( yet ) mature enough for large wholesale payment systems. see bank of japan and ecb ( 2017 ), “ payment systems : liquidity saving mechanisms in a distributed ledger environment ”, report on the stella project. 11 see committee on payments and market infrastructures and world bank group ( 2016 ), “ payment aspects of financial inclusion ”, bank for international settlements, april. 12 see, for example, “ we don ’ t take cash ’ : is this the future of money? ”, financial times, 10 may 2018. 13 source : bitcoin forum, 18 may 2010. 14 see heider, f., f. saidi and g. schepens ( 2018 ), “ life below zero : bank lending under negative policy rates ”, mimeo, available on ssrn. 15 for example, scalable deposit and withdrawal fees, as proposed by some academics, would allow cash to still 13 / 14 bis central bankers'speeches be used for small, necessary transactions while penalising large holdings more severely. see goodfriend, m. ( 2016 ), “ the case for unencumbering interest rate policy at the zero bound ”, prepared for the 2016 economic policy symposium proceedings, jackson hole : federal reserve bank of kansas city, 26 august ; agarwal, r. and m. kimball ( 2015 ), “ breaking through the zero lower bound ”, imf working paper no 15 / 224 ; and rogoff, k. ( 2014 ), “ costs and benefits to phasing out paper currency ”, nber working paper no 20126. 16 this analysis does not consider any potential disintermediation of the banking sector as a result of the introduction of a central bank digital currency. 17 see cœure,