“…Intuitively, an equilibrium in thin financial markets will be a triple consisting of a vector of asset prices, a profile of portfolios and a profile of price impact matrices, (P ,Θ,M ), such that: 1. all markets clear; 2. all traded portfolios are individually optimal, given the price impacts perceived by agents: for each trader i, at pricesP , tradeΘ i is optimal, given that any other trade,Θ i , would change prices toP +M i (Θ i −Θ i ); and 3. all perceived price impact matrices correctly estimate the effects of individual portfolio perturbations on the prices that would be required for the rest of the market to optimally absorb them: for each trader i, (small) perturbations to her portfolio, ∆ i , uniquely define a price at which the other traders of the market, given their price impacts, are willing to supply ∆ i to i, and the derivative of this mapping at equilibrium tradeΘ i isM i . 6 We take this vector as a column. 7 This means that the future numèraire wealth of investor i is given by e i + RΘ i , while the cost of her portfolio, if she constitutes it at pricesP , isP · Θ i , which she incurs in the first period.…”