The big players are vital - they interpret market events, react immediately and have access to related markets. It is not important at what price a bank purchases several thousand DEM from citizens, but at what price the big players exchange multi-million sums among themselves. Another problem is averaging. When the foreign currency was sold or bought is of vital importance to the exchange rate. If, for example, foreign currencies were predominantly bought, the kuna will be lower in two days time.
Fluctuations are of a statistical rather than market nature.
It can be argued that none of this carries much importance. Even with an exchange rate two days old and calculation technique plagued by statistical errors, it is only the CNB exchange rate. This is still accurate for accounting, customs and statistical purposes and decently represents the forex situation. A better indicator of kuna value can always be found on exchange rate lists supplied by commercial banks or through the forex services of a commercial bank. No one wants to criticize the Central Bank here.