Calculation:
For City P:
In 2015, the population increased by (45-40)/40 × 100% = 12.5%
In 2016, the population increased by (60-45)/45 × 100% = 33.33%
In 2017, the population decreased by (50-60)/60 × 100% = -16.67%
In 2018, the population increased by (70-50)/50 × 100% = 40%
In 2019, the population decreased by (65-70)/70 × 100% = -7.14%
In 2020, the population increased by (80-65)/65 × 100% = 23.08%
For City Q:
In 2015, the population increased by (30-20)/20 × 100% = 50%
In 2016, the population increased by (50-30)/30 × 100% = 66.67%
In 2017, the population increased by (55-50)/50 × 100% = 10%
In 2018, the population increased by (60-55)/55 × 100% = 9.09%
In 2019, the population increased by (70-60)/60 × 100% = 16.67%
In 2020, the population increased by (75-70)/70 × 100% = 7.14%
For City R:
In 2015, the population decreased by (40-50)/50 × 100% = -20%
In 2016, the population increased by (60-40)/40 × 100% = 50%
In 2017, the population increased by (70-60)/60 × 100% = 16.67%
In 2018, the population increased by (80-70)/70 × 100% = 14.29%
In 2019, the population increased by (90-80)/80 × 100% = 12.5%
In 2020, the population increased by (100-90)/90 × 100% = 11.11%
From the above calculations, we can see that City Q had the highest percentage rise in population from the previous year in the year 2016 with an increase of 66.67%.