The liquidity diversification can be measured by the liquidity score, defined here as the ratio between the pure market P&L CVaR and the market+liquidity P&L CVaR.
I have tried to reproduce the results in Meucci's paper A fully integrated liquidity and market risk model, for which the code is available in Matlab, more precisely Example 3 of the paper, the liquidity diversification. One would expect that with the same initial capital, varying the number of stocks (1, 5, 50 for example), the liquidity score increases, albeit not greatly because liquidity is less diversifiable than market risk. When I compute the liquidity score however, I don't get an increase but a decrease of the liquidity score. Did someone try his hands on this ? The first picture is for the portfolio with one stock, the second with 20 equally-weighted stocks. You can already see on the plots that the liquidity score for the portfolio of 20 stocks (LS = 0.4) will be lower than the portfolio with one stock (LS = 0.6). If you need the code for computing the liquidity score (not provided in Meucci's code), I can share it !