1911 Census of England and Wales, General Report with Appendices, Table 133: " Proportions per 1,000 persons speaking English and Welsh respectively, inclusive of those speaking both languages, 1901 and 1911; and ratios per cent. of proportions in 1911 to those in 1901: in Administrative Counties and County Boroughs".

COUNTIES AND COUNTY BOROUGHS. Speaking English. Speaking Welsh. Speaking both languages.
1901. 1911. Ratio. 1901. 1911. Ratio. 1901. 1911. Ratio.
Wales and Monmouthshire 846 887 105 499 435 87 348 350 101
                 
Monmouthshire (including County
    Borough)
990 955 96 130 96 74 123 92 75
  Monmouth Administrative County 989 953 96 157 116 74 148 111 75
  Newport County Borough 994 965 97 37 26 70 36 26 72
Glamorganshire (including County
    Boroughs)
928 939 101 435 381 88 369 350 95
  Glamorgan Administrative County 905 936 103 548 463 84 457 424 93
  Cardiff County Borough 987 950 96 51 67 83 79 65 82
  Merthyr Tydfil County Borough 923 948 103 571 502 88 498 467 94
  Swansea County Borough 959 941 98 324 271 84 291 252 87
Anglesey 517 610 118 917 887 97 437 525 120
Brecknockshire 906 929 103 459 415 90 366 359 98
Cardiganshire 493 641 130 930 896 96 426 554 130
Carmarthenshire 643 778 121 904 849 94 548 644 118
Carnarvonshire 522 622 119 896 856 96 419 500 119
Denbighshire 816 883 108 619 567 92 436 466 107
Flintshire 924 942 102 491 422 86 416 388 93
Merionethshire 493 613 124 937 903 96 431 536 124
Montgomeryshire 843 881 105 475 448 94 319 341 107
Pembrokeshire 880 900 102 344 324 94 225 247 110
Radnorshire 997 987 99 62 54 87 60 53 88