Populations in all municipalities except Warrnambool City and Moyne Shire shrank during the decade from 2001 to 2011, with Corangamite experiencing the biggest fall of six per cent, or 1054 fewer people. In total there were 2652 less people in the rural regions.

Defying that trend was Warrnambool, where the population grew by 10 per cent, or 2963, to a total of 32,592.

Moyne’s population rose 2.6 per cent in the decade by 412 to 16,175, with major towns Port Fairy having 3094 residents, Koroit 1958 and Mortlake 1073.

Glenelg Shire’s population fell 2.7 per cent to 19,843, with Portland’s 0.8 per cent growth taking it to 10,800.

In Southern Grampians Shire the overall population contracted 3.6 per cent to 16,510, and Hamilton fell 3.2 per cent to 9116 people.

Colac Otway Shire’s population was down two per cent to 20,578, but the main centre of Colac grew two per cent to 11,425. 

While Warrnambool’s growth over the decade looks impressive on paper, a closer examination of statistics reveals an unexplained slowdown since the 2006 Census despite booming building figures.

Between 2001 and 2006 the population rose by 2000, an average of 400 a year.

However, in the latter period official figures show it rose by only 1000, meaning the yearly average had halved to 200 a year.

City council leaders are puzzled by the statistical hiccup after Warrnambool had been widely touted as one of the state’s fastest-growing regional centres and on target to reach 50,000 by 2030.

The Bureau of Statistics’ pre-Census estimate looked healthier at 34,193, but this had to be revised when the adjusted figures came in.

Across Victoria the statistical adjustment wiped 86,700 from the state’s population.

City council executive research officer Andrew Paton said some explanation for the downward revision might be due to methodological differences between the two census years, 2006 and 2011.

“There remains considerable interpretation still to be done on this data to fully understand the 32,592 number and what it means for Warrnambool,” he said.

“All other data on labour, building permits, new housing etc is still pointing to considerable growth.

“It is important to emphasise that the post-Census 32,592 is still good news that Warrnambool is still growing — it’s just that the city is now coming off a slightly lower base number than previously thought.”

During the past two financial years 530 new residential dwellings were approved in Warrnambool, but there were only an extra 277 people living in the city. 

Mr Paton said that broadly translated to one new person for every two new homes approved.

“This is curious data and there are many variables and methodology issues that might explain it.”