The controversial plan to privatise bus services in Sydney’s inner west – which prompted a strike that disrupted travel for thousands of commuters – has focused attention on the standard of service on offer.

Under the proposal outlined by the state transport minister, Andrew Constance, the government would continue to own buses and depots, as well as set timetables and regulate fares in the area – known as region six.

Constance singled out poor performance in the area in the statement announcing privatisation, saying inner west services had attracted the highest number of complaints in the Sydney metropolitan area in recent years – above the results of bordering regions operated by private industry – and had one of the worst results for punctuality last year.

But analysis by Guardian Australia shows that the inner west is not the worst for complaints once the number of passengers is taken into account.

While the area does have the highest number of complaints on average over the past three years, this doesn’t take into account the number of people using the service.

Using Opal data on trips for each contract region, we can adjust the number of complaints to get a figure of complaints per 1,000 trips. This shows that the worst region is region seven, which covers the inner north areas of Epping, Chatswood and other suburbs:

complaints table

There has been no move to privatise services in this region.

Constance responded to the analysis by maintaining the State Transit Authority (STA) was not providing a decent service in the inner west.

“No matter which way you cut the numbers, the inner west bus service run by STA is not good enough,” he said. “This region had the worst on-time running performance last year and the highest total number of complaints since 2012.

“Of the top 40 most complained about bus routes, which contribute to a quarter of all bus complaints, region six bus routes are overrepresented.”

Charting the number of complaints against the number of trips also suggests that the number of complaints about buses in the inner west region is broadly in line with what you’d expect based on the other Sydney regions. The only outlier is region nine, which covers the eastern suburbs of Sydney:

chart complaints versus trips

Complaints aside, Constance is correct to say the inner west region does have the worst record for services on time over the past year:

table by region

However, there’s very little difference between region six and region seven, with only 0.3% separating the two. All the top four regions are run by STA, but the top four regions also represent what are likely to be the most congested regions.

The inner west region also happens to be the STA bus contract area that contains the fewest Liberal-held electorates:

bus map

The premier, Gladys Berejiklian, has denied that privatising the inner west region – as opposed to the northern or eastern regions – is about politics.

Geoffrey Clifton, a researcher focusing on public transport at the University of Sydney’s business school, agreed that inner west region buses had a mixed record.

“The question is to what extent would another operator be able to deliver an improved level of service at a lower cost to taxpayers?” he said.

“The evidence from most of Australia and from Europe and the UK is that governments are better at setting the timetable and service standards and the private sector is better at delivering those services in a cost-effective manner.”

“A smart operator should also be able improve on-time running and reduce the number of complaints despite the congestion. However, to make the most of this opportunity, we need the government to simplify the bus network, making services shorter and more direct to minimise the impact of congestion.”

The transport minister also suggested that private businesses could deliver a better service for less money.

“An STA bus runs at $8.94 per kilometre compared to a private bus operator at $5.43 per kilometre – taxpayers are being ripped off,” he said. “Recent examples in Sydney and the regions show that introducing competitive tendering for bus services delivers significantly more and better services for customers.”