Datasets were obtained from 73 centres (initial N=160,330). In France it is prohibited by law to record ethnicity; as a result 63,031 records known to be of mixed ethnic population could not be included in the final analyses. In the remaining datasets, ethnicity could not be traced in an additional 834 cases. In 805 cases data were discarded because they comprised subjects with suspected asthma. In 123 cases data could not be used to derive reference values because forced expiratory time was < 1 s. Records with transcription errors that could not be resolved, with missing values for sex, age, height, FEV1 or FVC, or where the FEV1/FVC ratio was >1.0 were discarded. Since virtually all data had been previously used in publications, there were very few errors. Datasets from India, Pakistan, Iran, Oman, the Philippines and South Africa were either too small in number for analysis, or could not be combined into groups with other sets (N=17,341). One dataset (N=3483) could not be used until the data had first been published by the authors. As the statistical analyses are sensitive to outliers, in subsequent analyses data points that yielded a z-score <−5.0 or >5.0 were identified as outliers (N=526) and excluded from further analyses. This left data on 31,856 males and 42,331 females aged 2.5–95 years (Figure 1, online supplement (OLS) tables E1, E2 and E3).