Table shows year wise road accidents registered in a city during 2015 – 2018.
| Years | Accidents | |||
| Minor | Injury | Serious | Casualties | |
| 2015 | 160 | 125 | 55 | 30 |
| 2016 | 150 | 120 | 50 | 35 |
| 2017 | 210 | 170 | 30 | 25 |
| 2018 | 190 | 130 | 60 | 40 |
What is the percentage reduction in serious from the year 2016 to 2017?