  In this work, we provide a framework linking microstructural properties of an
asset to the tick value of the exchange. In particular, we bring to light a
quantity, referred to as implicit spread, playing the role of spread for large
tick assets, for which the effective spread is almost always equal to one tick.
The relevance of this new parameter is shown both empirically and
theoretically. This implicit spread allows us to quantify the tick sizes of
large tick assets and to define a notion of optimal tick size. Moreover, our
results open the possibility of forecasting the behavior of relevant market
quantities after a change in the tick value and to give a way to modify it in
order to reach an optimal tick size.
