Alarming declines in patronage on Auckland ferries have been blamed on a double-counting blooper stretching back to 2011.
Passengers arriving at the Downtown ferry terminal on alternating indirect Fullers ferry trips from Waiheke via Devonport were counted twice, until the error was picked up late last year by a new employee of the ferry company.
But the newcomer rectified the error for monthly reporting purposes without telling anyone else, says chief operations officer Greg Edmonds.
The unannounced reversion to the correct script meant ferry patronage in January suffered by comparison with an inflated figure for the same month of last year.
It appeared to have fallen by 10 per cent, and by an even more dramatic 16 per cent in February, prompting Mr Edmonds to order an investigation.