In pricing theory, the scarcity principle suggests that the price for a scarce good should rise until an equilibrium is reached between supply and demand. However, this would result in the restricted exclusion of the good only to those who can afford it.
Children aged between three and seven should be limited to half-an-hour to an hour of screen time each day, he said. Those aged seven to 12 should spend just one hour in front of screens. Children aged 12 to 15 should have a maximum of 1.5 hours in front of screens and those aged 16 and over should spend just two hours, he recommends. ''Reducing total daily screen time for children, and delaying the age at which they start, could provide significant advantages for their health and wellbeing,'' he writes.
The amount of time children spend glued to a screen has risen dramatically in the last 20 years, a new report suggests. Children aged five to 16 spend an average of six and a half hours a day in front of a screen compared with around three hours in 1995, according to market research firm Childwise. Teenaged boys spend the longest, with an average of eight hours. Eight-year-old girls spend the least - three-and-a-half hours, according to the study. Screen time is made up of time spent watching TV, playing games consoles, using a mobile, computer or tablet.