This Electronic Supplementary Material (ESM) contains two parts. Section S.1 complements Section B of the paper by providing an exhaustive proof of Proposition 1 with all technical details included. Section S.2 provides the proof of Proposition 4.
To avoid confusion in the numbering of equations and sections between the main text and this ESM, all numbers in the ESM will be prefixed by “S”. Conversely, numbers without prefix refer to an equation or a section of the main text.