Canadians say the single most important issue in this election campaign is the economy, with the environment coming second, according to the latest results from Vote Compass, CBC's online voter engagement survey.

The findings emerge at the halfway mark of the 2015 campaign, an unusually long one that began on Aug. 2 and reaches its climax election night on Oct. 19.

When asked, "What issue is most important to you in this election?" 36 per cent of Vote Compass respondents said "economy," by far the most frequently cited issue.

"Environment" is second with 11.3 per cent, followed by "health" with 10.5 per cent. Rounding out the top five are "accountability" (7.1 per cent) and "taxes" (5.6 per cent).

The findings are based on data from 164,704 respondents who participated in Vote Compass from Aug. 29 to Sept. 1.

The results of this survey weren't based on existing categories, but rather issues self-identified by respondents, says Clifton van der Linden, founder and director of Vox Pop Labs, which created Vote Compass.

"Other polls will choose the themes or issues users can select from. But because [Vote Compass has] such a large data set and number of respondents, users were free to decide, in the absence of any constraints, what issue was important to them," says van der Linden.

Éric Grenier, founder of ThreeHundredEight.com, a website dedicated to political polling in Canada, says that the economy is always a top issue — if not the top issue — on the minds of voters.

He says the relative prominence of the environment in this survey, however, "is a little bit surprising."

Penny Collenette, who worked in the Prime Minister's Office under Jean Chrétien, says the ascendance of the environment as a major voter issue is a new development.

"I don't think that the environment would have been pegged second several years ago," says Collenette, who ran as a Liberal Party candidate in 2008 and is now an adjunct law professor at the University of Ottawa.

Awareness of climate change

Van der Linden confirms that the economy and the environment have become more prominent issues since the 2011 federal election, when Vote Compass conducted a similar survey.

In the 2011 survey, van der Linden says, the top five results were the economy (31 per cent), health care (11.5 per cent), government accountability (11.4 per cent), environment (7.8 per cent) and partisan comments (5.9 per cent).

Collenette believes a number of factors may be responsible for making the environment a more salient campaign issue this time around, including greater awareness of the extent of oilsands development in Alberta and reports of extreme weather in Canada and around the world.

The overall findings for the latest Vote Compass survey break down a little differently when age, gender and party preference are taken into account.

For example, 35 per cent of respondents 55 years and older identified the economy as the No. 1 issue, while only 29 per cent of 18- to 34-year-olds did the same.

Meanwhile, 15 per cent of 18- to 34-year-olds determined the environment was most important, while only nine per cent of people aged 55 and older felt the same way.

In terms of party preference, 56 per cent of Conservative voters identified the economy as the main issue, while only 17 per cent of Green Party supporters did the same. Conversely, 42 per cent of Green Party voters put the environment at the top of the list, while only three per cent of Conservative supporters did the same.

While these findings demonstrate evolution in voter thinking since 2011, Collenette says this snapshot doesn't reflect some of the issues that have emerged in the most recent weeks of the campaign.

"What's missing are some buzzwords — deficit, child care, refugees and pensions," she says.

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Developed by a team of social and statistical scientists from Vox Pop Labs, Vote Compass is a civic engagement application offered in Canada exclusively by CBC News. The above findings are based on 164,704 respondents who participated in Vote Compass from Aug. to Sept. 1, 2015.

Unlike online opinion polls, respondents to Vote Compass are not pre-selected. Similar to opinion polls, however, the data are a non-random sample from the population and have been weighted in order to approximate a representative sample. Vote Compass data have been weighted by geography, gender, age, educational attainment, occupation, religion, religiosity and civic engagement to ensure the sample's composition reflects that of the actual population of Canada according to census data and other population estimates.