"The 2010 National Profile reported 6,866 offences of commercial cultivation in 2009/10, increasing by 15 per cent over the following two years.3 Based on those forces that provided three years’ data for this profile, there was a 3.7 per cent reduction between 2011/12 and 2012/13 and a 5.6 per cent reduction between 2012/13 and 2013/14. These figures equate to an annual average of five offences recorded per 100,000 population.
"Seasonal trends in reporting were not identified. This is understandable as cannabis production is not driven by external environmental factors.
Of those forces reporting increased offences, some have dedicated dismantling teams and forensic strategies in place to identify farms and recover plants. These specialist teams provide detailed local profiles; identify intelligence links and offenders; and ascertain the source of the equipment used. This is likely to have prompted their increased recording.
"During the three year period, 6,010 offenders were identified as involved in the commercial cultivation of cannabis.4 Offenders continue to be predominantly male5, accounting for 88.5 per cent of all offenders, and largely white North European (70 per cent of all offenders) 6 most frequently aged between 25 and 34. There has been a decline in the proportion of South East Asian offenders over the last three years, now representing approximately 12 per cent of all offenders recorded7.

Source

National Police Chiefs' Council, "UK National Problem Profile: Commercial Cultivation of Cannabis 2012" (London, England: 2015), p. 6.
http://www.npcc.police.uk/Pub…