The information requested falls within the responsibility of the UK Statistics Authority. I have asked the authority to reply.
Letter from Karen Dunnell, dated January 2009:
As National Statistician I have been asked to reply to your question regarding how many (a) male and (b) female 18-year-olds there were in each year since 2005 and what the Office for National Statistics projects the number of 18-year-olds to be in each year to 2015. (247129)
The table below shows the United Kingdom population of males and females aged 18 for each year from 2005 to 2015. The figures up to and including 2007 are population estimates. The most recent national population projections, based on the population at the middle of 2006, have been used to provide the estimated population aged 18 from 2008 to 2015.
Thousand Population aged 18 Males Females Population estimates 2005 405 385 2006 417 392 2007 412 388 Population projections1 2008 417 392 2009 423 396 2010 415 391 2011 403 377 2012 398 372 2013 389 364 2014 386 362 2015 389 365 1 2006-based national population projections, ONS