The chart shows the results of surveys in one African country asking teenagers the main reasons for using their phones between 2016 and 2019

The given pie charts illustrate the data of researches in an African country about what teenagers use their phones for over a period from 2016 to 2019.
It is clear that the figures stabilized in the first 3 years and changed remarkably in the last year.
In 2016, the proportion of social networks dominated half of the chart then dropped slightly to 48 percent in 2017 and raised again in the next two year and reached 56 percent, which is the highest of all charts. The camera usage's percentage stayed unchanged in the first half of the period with 15 percent then increased in the other half. The email features reduced through all the years from 25 percent to 19 percent. Phone calls group fluctuated between 10 percent and 13 percent in 2016 to 2018 then sinked sharply in 2019 to only 5 percent which makes it becomes the lowest figure in all the pie charts.