[General Election Poll Verification - Dongjak-eul] 17 Surveys from March to April... Only 1 Correct Prediction for Both Lee Su-jin and Na Kyung-won Vote Shares

[Asia Economy Reporter Jin-Young Hwang] Various opinion polls conducted to gauge local public sentiment ahead of the general election have been mired in controversy. The core of the debate was that opinion polls failed to accurately capture public sentiment and instead distorted public opinion. Asia Economy is publishing a series verifying how accurate the opinion polls were, focusing on constituencies where many polls were conducted.

The Seoul Dongjak-eul district, where Lee Su-jin of the Democratic Party of Korea and Na Kyung-won of the United Future Party competed, drew attention as a contest between female judges who graduated from Seoul National University.

The Democratic Party, struggling to find a candidate to challenge Na, who was seeking a fifth term, nominated Lee, whose pre-political career was similar to Na’s.

Contrary to expectations that Na, who had solidified her voter base through consecutive re-elections in this area, would have the upper hand, opinion polls showed the political newcomer Lee leading.

After the official campaign started on the 2nd, some polls showed Na trailing or overtaking Lee within the margin of error, but the final result was Lee’s victory.

Lee Su-jin received 61,407 votes (52.1%), Na Kyung-won 53,026 votes (45.0%).

The vote difference between Lee and Na was 8,381 votes (7.1 percentage points), a relatively large margin for a closely contested district.

According to the Central Election Poll Deliberation Commission on the 23rd, 17 opinion polls were conducted since March to gauge the political landscape in Dongjak-eul, commissioned by media outlets.

Seven of these polls were conducted during the official campaign period. (See table)

Opinion polls conducted in April in Dongjak-eul (unit: %)

The only poll that accurately predicted both candidates’ vote shares within the margin of error was the one conducted by News Tomato, commissioned to the Korea Society Opinion Institute (KSOI) on the 7th.

This poll surveyed 518 men and women aged 18 and over residing in Seoul Dongjak-eul using a 100% wireless ARS automated response method, showing Lee Su-jin at 48.4% and Na Kyung-won at 42.1%. (For detailed information, refer to the Central Election Poll Deliberation Commission website.)

The difference between the poll and actual vote shares was 3.7 percentage points for Lee and 2.9 percentage points for Na, both within the margin of error (±4.3 percentage points).

The support gap between the two candidates was 6.3 percentage points, very close to the actual vote difference of 7.1 percentage points, demonstrating high accuracy.

Among the seven polls conducted in April, six correctly predicted the winner, but the poll commissioned by CBS and Kukmin Ilbo to Jowon CNI, conducted on the 4th and 5th, showed Na leading within the margin of error (±4.4 percentage points).

This poll showed Lee Su-jin at 40.9% and Na Kyung-won at 44.1%, indicating Na leading within the margin of error.

This poll had the highest proportion of landline phone surveys at 31% among Dongjak-eul polls conducted in March and April.

When the proportion of landline phone surveys increases, opinions of voters aged 60 and over are better reflected, typically raising conservative candidate support and lowering progressive candidate support.

The support rate for Lee in this poll was the lowest among the seven polls conducted in April, while Na’s support rate was the highest.

This poll’s result was close to Na’s actual vote share with only a 0.9 percentage point difference but differed from Lee’s actual vote share by 11.2 percentage points.

Due to the more than 10 percentage point difference from Lee’s actual vote share, the poll produced a reversed outcome between winner and loser.

Among the seven April polls, five accurately predicted Lee’s support rate within the margin of error, while only three did so for Na’s support rate.

The poll conducted by SBS, commissioned to Ipsos from the 5th to 8th, showed Lee Su-jin at 52.9% and Na Kyung-won at 36.6%, with Lee’s support rate differing from the actual vote share by only 0.8 percentage points.

However, Na’s support rate differed from the actual vote share by -8.4 percentage points, far outside the margin of error.

Previously, in the verification of general election polls in Jongno and Seoul Gwangjin-eul, the Democratic Party candidates’ vote shares were generally predicted within the margin of error, but the United Future Party candidates’ vote shares often fell outside the margin of error.

Also, when the proportion of landline phone surveys was raised to around 30%, the United Future Party candidates’ vote shares were quite close to actual results, but the Democratic Party candidates’ vote shares were consistently underestimated by more than 10 percentage points.

Among the ten polls conducted in March, nine predicted Lee Su-jin’s victory, but the poll commissioned by JoongAng Ilbo to Ipsos on the 13th and 14th showed Na leading Lee narrowly with 36.6% to 36.2%.