I trade thin liquidity NYSE issues, and the price improvement "algorithm" is running rampant these days. More than I have ever seen, and more than what the NYSE website claims (on the order of 40 % or so).
This so-called "price improvement" that NYSE allows for, provides
for penny (or more) improvements for those who are already willing to pay the "market" price for a stock, and causes "price
disimprovement" for those that are posting limit orders, and are
jumped in front of. This clearly disrupts the laws of supply and
demand in the marketplace, and diminishes the usefulness of
placing limit orders into the system. This results in diminished
confidence in the marketplace by those placing limit orders, which
will inevitably result in fewer limit order being placed. This will
ultimately (and has already) diminished the liquidity in the marketplace, IMO. Why does someone who wants to buy at the market in the first place get a price improvement, while those who want to buy a t a limit price, continuously get price disimproved, via unfilled orders ? I just don't get this one........another "feature" of a totally antiquated market (NYSE).
I truly believe that "price improvement" was devised by Grasso and company, in an attempt to rid the marketplace of Day Traders. What he is forgetting is that Day Traders contribute positively to liquidity, and Specialists are Day Traders, whose # 1 goal is to make money first; regulate the market 2nd (Grasso himself today said that his job of market regulation is only 1/3 of his job......). Enough said !