Offer your thoughts or opinion on the input financial query or topic using your financial background.

Why liquidity implies tight spread and low slippage
Theoretically, it's a question of rate of return. If a desired or acceptable rate of return for market makers' capital is X, and X is determined by the product of margin & turnover then higher turnover means lower margin for a constant X.  Margin, in the case of trading, is the bid/ask spread, and turnover, in the case of trading, is volume. Empirically, it has been noted in the last markets still offering such wide-varying evidence, equity options: http://faculty.baruch.cuny.edu/lwu/890/mayhew_jf2002.pdf