The 50 HK cents in cab fare change most taxi drivers routinely keep without asking can add up - to millions.
HK$2.28 million, in fact. That is the total in automatic tips that drivers of the 15,250 red urban taxis in Hong Kong are estimated to have retained since a new fare structure was introduced in December 2008.
Under the new system, many fares now end in 50 cents, which is regularly rounded up to the next dollar when the cabbie gives change.
'On nine out of 10 journeys, the taxi drivers do not give me back the 50 cents,' a regular cab rider surnamed Yuen said. 'I don't want to ask for it, but sometimes I wonder if the drivers are supposed to give it back. It is my money, after all.'
Yuen, an office worker in Causeway Bay, said out of the 15 taxi journeys she took last month for which she kept a receipt, on only one did the driver give her back the 50 cents.
'I was so surprised when he gave me back the change,' she said.
A Post found that 16 of the 20 cab rides he took over the past two weeks had a fare ending in 50 cents. Only one driver bothered to return the change.
The new fare structure raised fares for short-haul trips and cut those on long-haul journeys.
After a flag-fall charge of HK$18 for the first two kilometres, an urban taxi's meter jumps HK$1.50 per 200 metres; once it reaches HK$70.50, each jump is HK$1.
Counting the jumps on the meter shows that 90 per cent of urban cab trips costing less than HK$200 now have fares ending in half a dollar.
According to government statistics, a monthly average of 954,200 taxi trips were taken last year, and 84 per cent - about 800,000 - were in the red urban cabs. Of these, about 65 per cent, or 520,000, were middle-haul journeys that cost between HK$19.50 and HK$70.50, while a further 15 per cent, or 120,000 trips, cost more than HK$70.50.
About half of the middle-haul journeys and all the long-haul rides - totalling about 380,000 - had fares ending in 50 cents. If drivers on 80 per cent of these trips kept the 50 cents, it would add up to total extra income of HK$152,000 a month, or HK$2.28 million since December 2008.
A driver who takes 30 hires a day and keeps the change 80 per cent of the time could gain HK$171 a month in additional income.
Kwok Chi-piu of the Urban Taxi Drivers Association Joint Committee, one of 27 taxi groups that agreed on the new fare structure, said fares were rounded to whole dollars or amounts ending in 50 cents so as to make giving change easier.
'Some drivers said at the time that handling change of 20 cents and 10 cents was very troublesome, and they preferred fares to be rounded off to 50 cents because the 50-cent coin is more commonly used,' Kwok said.
Low Shih-cheng, a veteran taxi driver and deputy director of the taxi branch of the Motor Transport Workers General Union - another group that voted for the plan - said while there was a decade-old understanding between drivers and passengers that fares ending in 20 cents or 10 cents should be rounded off, drivers were supposed to give back change of 50 cents or more.
'Unless passengers don't accept it, we must give the change,' he said.
Several regular taxi travellers say they have noticed fewer drivers keeping 50-cent coins in their coin boxes.
Road traffic regulations require cab drivers to carry change of at least HK$10 in coins of HK$1 or less.
Low said he and his colleagues had found it difficult lately to obtain 50-cent coins from banks, where there had been a recent shortage.
However, he admitted some drivers were simply greedy.
'A reason why taxis remain the only type of public transportation that doesn't accept Octopus card payments is that taxi drivers don't want to give up the change,' he said.
The fact that an Octopus card reader costs HK$10 a day to rent is another reason the payment system has not been welcomed by the trade.
The Transport Department said drivers should charge according to the meter and should heed the passengers' requests for change as far as possible.
Number of urban taxi journeys every month: 800,000
Percentage of fares below HK$200 which end with odd 50 cents: 90
Extra amount paid every month if change not returned on 80% of trips: HK$152,000
Pontential extra monthly income per driver: HK$171