Below are results from the 2003 and 2011 English skills for life survey. Literacy and Numeracy were measured for the age 16 to 65 population. (Here.) Annoyingly, only %s by skill level were given. Moreover, the distributions was highly unnormal. This was unfortunate since the Literacy and Numeracy tests seemed to have been good measures of ability. To extract a d-vale, I compared the percent of Whites who fell above the skill level where approximately 50% of Whites fell to the % of Black Caribbeans who fell at and below this level. If you can think of a better method, feel free to offer it. I only compared Whites with BC because these were the only groups for which the English as first language rates were above 90%. The d-value came out to 0.77. I estimated a composite d-value of 0.86.