The three companies use differing methodologies in coming up with their ratings

Norstat, which produces weekly aggregated ratings on behalf of conservative think-tank  the Institute for Social Research  (MTÜ Ühiskonnauuringute Instituut), primarily utilizes over-the-phone surveys, the internet polls are also taken.

Turu-uuringute says it splits its interviewees 50-50 between face-to-face respondents and those online, though more recently it has replaced the in-person surveys with phone calls as well.

Kantar Emor is online-only.

The principle of aggregating ratings is widely used internationally. Differences between the various methods of taking surveys may also translate into differing results, since, it is widely thought, older people are less likely to use online surveys, while at the same time these offer greater anonymity than, say, a face-to-face questionnaire, which can also have an effect at the margins regaring those parties or views seen to be on the fringe or at least controversial.

The coronavirus and its restrictions have also meant face-to-face polls have been mostly shelved.

With that in mind, Eesti 200 – a party founded in 2018 which is contesting its third election in October – polled at 15 percent support across all three companies' ratings, with SDE and Isamaa picking up 9 percent and 6 percent respectively.

All three of these figures represent an increase on recent weeks, and are particularly significant for Isamaa, which has faced internal division lately and which was hovering around the 5 percent-mark at one point.

Under Estonia's modified d'Hondt system of proportional representation, 5 percent is the minimum amount of votes required to win any seats in a given constituency.

Reform (Reformierakond), the largest party by MPs at the 101-seat Riigikogu (34) saw a slight fall to 28 percent on aggregate, while EKRE, which has been seeing a rise in support as a whole this year, fell slightly to 20 percent in May.

This is still ahead of Center (Keskerakond) on 19 percent, meaning EKRE is still slightly ahead of Center at the polls. The party's socially conservative stances are likely to appeal to some more conservative Center voters.

The other two major parties, the Estonian Greens (Rohelised) and TULE, polled at two percent and one percent respectively. Neither party has any Riigikogu representation at present (the Greens have in the past), while TULE was formed last year via a merger of the Free Party – which had half-a-dozen seats at the last Riigikogu composition – and Richness of Life, a broadly eco- and subsidiarity-focused party founded in 2018.

Of differences of any significance between Norstat, Kantar Emor and Turu-uurigute's results, Reform and Eesti 200 are the most affected.

Reform picked up more support with Norstat than with the other two, while Eesti 200 fared worse with Norstat.

This is particularly significant since the electoral base of both – often younger, urban, socially liberal professionals – have some cross-over.

Meanwhile, Kantar Emor puts SDE and Isamaa on higher support levels than Norstat and Turu-uuringute do; there is nothing to choose from between the three apropos Center and EKRE support levels.

The breakdown by party in March, April and May is below.

 ERR's online news in Estonian started publishing the aggregated poll results last August. The margin of error of the results from each firm in isolation can be as high as 3 percent, ERR says.

The next elections are to the local municipalities on October 17.

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