Unfortunately, West Yorkshire Police are unable to provide you with the information requested. 
 
It is estimated that the cost of providing / locating the information you seek within your request, would exceed the time threshold. When a reasonable estimate has been made that the appropriate limit would be exceeded, there are no requirements for a public authority to undertake the work.
 
Please see Appendix A, for the full legislative explanation as to why West Yorkshire Police are unable to provide the information. 
 
If you would like to refine or narrow the scope of your request, West Yorkshire Police will assist you in negotiating the possibility of the provisions, of the information requested. Please see the Advice and Assistance, under Section 16 of Appendix A. 

Appendix A
 

The Freedom of Information Act 2000 creates a statutory right of access to information held by public Authorities. A public authority in receipt of a request must, if permitted, state under Section 1(a) of the Act, whether it holds the requested information. If held then this information will be communicated to the applicant under Section 1(b) of the Act. 
 
The right of access to information is not without exception and is subject to a number of exemptions. Which are designed to enable public authorities to withhold information that is unsuitable for release.
  
Importantly the Act is designed to place information into the public domain, that is, once access to  information is granted to one person under the Act, it is then considered public information and must  be communicated to any individual should a request be received. 
 
DECISION 
 
This letter serves as a Refusal Notice under Section 17 of the Freedom of Information Act 2000.   
 
Section 17 of the Act provides: 
 
(1)  A public authority which, in relation to any request for information, is to any extent relying on a claim that information is exempt information must, within the time for complying with Section 1(1), given to the applicant a notice which:- 
 
(a) States the fact, 
(b) Specifies the exemption in question, and 
(c) States (if that would not otherwise be apparent) why the exemption applies. 
 
REASONS FOR DECISION 
 
The reason that we are unable to provide you with this information is covered by the following  exemption(s): 
 
Section 12 - Where the cost of compliance exceeds the appropriate limit 
 
West Yorkshire Police can confirm that we hold the information you seek, however it is not held in an easily retrievable format. 
 
In order to establish the number of individuals arrested who have raised the statutory defence under section 45 of the Modern Slavery Act would involve a manual search of all investigations that contain the notes for keywords ‘Section 45’. For the requested time frame there are 266 records containing ‘Section 45’ at an estimate of 5 minutes per record this would take 22 hours to establish if this was relevant to the request. 

In relation to question 2 there were 139 crimes linked to arrests made under the Modern Slavery Act 2015, and we would need to review any crimes linked to each of these (as a victim of criminal exploitation may actually be linked as an offender on a related crime record). At an estimate of 10 minutes per record this would take an additional 23 hours to provide. 

In relation to question 3, there were 497 illegal cultivation of cannabis crimes, in order to establish if any of these had linked investigations as outlined would involve a manual search of each crime. At a conservative estimate of 5 minutes per record this would take an additional 41 hours to provide.

It has been estimated that the cost of providing you with this information is above the amount to which we are legally required to respond i.e. the cost of locating and retrieving the information exceeds the 'appropriate level' as stated in the Freedom of Information (Fees and Appropriate Limit) Regulations 2004, which currently stands at £450 worth of work. 
 
Our ACPO guidance states that we do not issue fees notices and therefore in accordance with the Freedom of Information Act 2000, this letter acts as a Refusal Notice. 
 
West Yorkshire Police have utilised Section 12, which states "A public authority does not have to comply with a request for information if the cost of compliance exceeds the appropriate limit", this is further affirmed by the Decision Notice issued by the Information Commissioner's Office (Reference: FS50143930), and Guidance issued by the Information Commissioner's Office on Using the Fees Regulations. 
 

ADVICE AND ASSISTANCE 
 
Under Section 16 of the Freedom of Information Act 2000, my duty to provide advice and assistance to persons who have made request for information, please be advised that West Yorkshire Police can offer the following advice as to how to refine your request: 
 
We may be able to provide you with a response to question 4 of your request.

You may also find the following links useful to your request:

Modern Slavery:
Freedom Of Information - Disclosure Log | West Yorkshire Police

Cannabis:
Freedom Of Information - Disclosure Log | West Yorkshire Police
 
Please note that police forces do not use generic systems or identical procedures for capturing the data.  For these reasons this response to your questions should not be used for comparison purposes with responses you may receive from other police forces.