# Data Sources and Composition

The dataset contains **18,935,335 directional translation examples** across 21 source pools. Percentages below are calculated from the final example counts, not token counts or unique bilingual pairs.

| Source | Examples | Share |
|---|---:|---:|
| UNPC | 3,704,842 | 19.566% |
| OpenSubtitles | 2,708,074 | 14.302% |
| MultiUN | 2,377,741 | 12.557% |
| CCMatrix | 1,580,197 | 8.345% |
| OPUS100 | 1,554,605 | 8.210% |
| WikiMatrix | 1,415,377 | 7.475% |
| CCAligned — additional OPUS pool (`opus_big_ccaligned`) | 1,080,624 | 5.707% |
| CCAligned (`ccaligned`) | 955,073 | 5.044% |
| News Commentary | 951,488 | 5.025% |
| CCMatrix — additional OPUS pool (`opus_big_ccmatrix`) | 764,627 | 4.038% |
| BWB | 486,810 | 2.571% |
| Wikimedia | 396,975 | 2.096% |
| TED2013 | 360,985 | 1.906% |
| WikiTitles | 293,505 | 1.550% |
| CoVoST2 | 232,457 | 1.228% |
| BSTC | 27,788 | 0.147% |
| TED2020 | 17,934 | 0.095% |
| QED | 13,955 | 0.074% |
| MASSIVE | 8,644 | 0.046% |
| Neulab TED Talks | 3,604 | 0.019% |
| ELRC Health | 30 | <0.001% |
| **Total** | **18,935,335** | **100%** |

## Translation Directions

| Direction | Examples | Share |
|---|---:|---:|
| English to Chinese | 10,106,394 | 53.373% |
| Chinese to English | 8,828,941 | 46.627% |

`src` identifies the source pool for each record. The additional OPUS pools are listed separately to match those labels. Percentages are rounded and may not sum to exactly 100%.