She said 31,933 people were charged in 2009 but the number dropped to 16,304 in 2016.
In Northland, drink-driving charges dropped 30 per cent whereas the number of such convictions plummeted 29 per cent during the five-year period.
The percentage decrease in the number of people charged with drink-driving in Northland was the second lowest behind Canterbury which recorded a 24 per cent drop.
All other regions performed better.
Figures supplied by the Ministry of Justice show 1480 people were charged with drink-driving in Northland in 2009, 1705 in 2010, 1574 in 2011, 1271 in 2012, 1139 in 2013, 1068 in 2014, 1009 in 2015, and 1033 last year.
Those convicted in Northland courts over the same period decreased from 1415 to 1002.
The statistics show the most serious drink-driving charges only and excludes those caught having an alcohol reading of between 250 and 400 micrograms per litre of breath who were issued with instant $250 fines.
"One person charged and convicted is one too many. At the end of the day, we're still seeing far too many fatal and serious accidents involving alcohol," Mr Ewers said.
He said any initiative such as the Stop Alcohol Impaired Drivers (SAID) and Drive Soba would help in raising awareness about the dangers of drink-driving.
"We're still seeing alcohol involved in vehicle crashes, particularly in rural areas.
"Awareness, education, and parents recognising their responsibility all play a part in addressing the issue," he said.
Most of those charged and convicted for drink-driving in Northland since 2009 were people under 25.
However, the number of convictions for that age group decreased 43 per cent and 60 per cent nationally.
Roadsafe Northland Whangarei and Kaipara road safety education programme manager Gillian Archer said worringly the rural population was not showing much improvement in terms of getting drink-driving convictions down.
She said the ministry figures understated the problem because only the most serious offence of drink-driving was recorded.
Neither she nor Mr Ewers were prepared to comment without studying the statistics on possible reasons why the percentage decrease in Northland was lower than the national figures.
The Government attributed a drop in charging and conviction rates to the Alcohol Reform Bill, a limit on alcohol promotions, zero alcohol limits for repeat offenders and drivers aged under 20, and mandatory alcohol interlocks for repeat offenders.