EL PAÍS and Cadena SER have made the complete internal data from their July monthly barometer, conducted by 40dB., publicly available. The release includes headline results on voting intentions and perceptions of justice in Spain, alongside the statistical documentation behind the findings. This includes the results report and questionnaire, with anonymized individual responses and detailed cross-tabulations completing the record. The files let readers examine the survey material and the basis for the published analysis.
The release also reflects a transparency practice highlighted by EL PAÍS data journalist and analyst Kiko Llaneras in a comparative assessment of Spanish polling firms. His analysis examined 44 elections since 2018, comparing poll estimates with official results, and treated the publication of respondent-level data as a criterion alongside poll accuracy, including ideological bias. Llaneras noted that 40dB. publishes its survey microdata consistently and promptly, allowing outside researchers to scrutinize the polling work.
The comparison measured accuracy through the average party-level error in percentage points and assessed whether polls overstated or understated the right’s advantage over the left. It included each firm’s final poll when fieldwork ended five to 41 days before voting. Parties receiving less than 2% of the vote were excluded from the error calculation, and general-election comparisons included only parties competing in more than ten provinces. The composite score weighted overall error at 44% and ideological bias at 33%; general-election performance and microdata publication each accounted for 11%, with the component weights rounded.
Llaneras’s analysis ranked GAD3 as the most accurate pollster overall in the dataset. IMOP came next, ahead of Sociométrica, with Sigma Dos following. For the three general elections included, but, 40dB. was the best-performing firm. Llaneras wrote that it “was the most accurate in all three general elections.” The assessment also found leftward overestimation in seven of 21 elections for 40dB. Across the broader comparisons, a leftward bias appeared in seven of ten, though it was neither universal nor large.
The July barometer covers voting intentions across Spain and public perceptions of the justice system. Making its questionnaires, anonymized responses and cross-tabulations available gives researchers and the public material to inspect the survey and conduct further analysis. The data release places the poll’s findings within a wider debate about transparency and accountability in public-opinion research.
Barometers conducted by 40dB. for EL PAÍS and Cadena SER track changes in political preferences and public attitudes. By opening the underlying files alongside its report, the July edition lets readers examine the published conclusions against the survey evidence and documentation behind them.
