Adjustments arising from temporary COEs that have expired or were cancelled. Formula Since the change in the total motor vehicle population is given by the number of registrations minus the number of de-registrations and any unallocated quota in a given year may be carried over to the following year, the quota formula is as follows: In the formula above, the subscript denotes calendar year and the subscript denotes quota year (May to April). Initially, projected deregistrations for (calendar) year were simply taken to be equal to actual deregistrations in but from quota year 1999–2000 onwards, a projected number of deregistrations has been used. Each year, the quota is set to allow for a targeted percent growth in the total motor vehicle population, plus additional quota licenses to cover the number of motor vehicles that will be deregistered during the (calendar) year, plus any unallocated quota licenses from the previous quota year. Validity The holder of a COE is allowed to own a vehicle for an initial period of 10 years, after which they must scrap or export their vehicle or bid for another COE at the prevailing rate if they wish to continue using their vehicle for an intended remaining lifespan. At the end of the 10-year COE period, vehicle owners may choose to deregister their vehicle or to revalidate their COEs for another 5-year or 10-year period by paying the Prevailing Quota Premium, which is the three-month moving average of the Quota Premium for the respective vehicle category. You do not need to bid for a new COE to renew the existing COE of your vehicle. A 5-year COE cannot be further renewed, which means that at the end of a 5-year COE, the vehicle will have to be de-registered and either scrapped or exported to another country other than Singapore. Depending on the value of the COE at the time of renewal vehicle owners are subjected to a somewhat emotional dilemma of whether to pay for a new COE which can amount to more than the market value of the vehicle or to deregister their vehicle. The emotional dilemma is certainly enhanced when the vehicle owner is forced to deregister and scrap an otherwise road worthy vehicle due to lack of time or insufficient funds to afford the COE at the prevailing rate. For comparison in terms of vehicle value to COE value a Second Hand 2007 Mercedes-Benz