28 March, 2022

Cambridge residents have their say on major new development

In February and March 2022 we recruited 18 participants for the Cambridge Core Site Ideas Exchange. These people will meet online and in person over the next two years to respond to the invitation to "Help shape our plans for a new district in North East Cambridge".

Developers TOWN commissioned the Ideas Exchange to get meaningful community input on a significant local development plan. The Core Site is the area currently mainly occupied by the Anglian Water’s Water Waste Treatment Plant and Cambridge City Council’s golf driving range, close to Cambridge North Station. Over the next two years, the appointed master-developers U+I and TOWN are creating proposals for 5,600 new homes as well as office, retail, community facilities and green outdoor space.

Below we briefly describe the details of this recruitment process; the process followed our standard two-stage sortition template in conformity with the OECD's good practice principles for deliberative processes for public decision making.

Stage 1

We randomly selected 6000 addresses from across North East Cambridge. Each of these addresses received a letter in the post inviting residents to sign up as potential members of the Ideas Exchange. We have learned from previous experience that people who live in more deprived areas tend to be less likely to respond to invitations of this kind, hence the random selection was weighted as follows: 80% of the addresses were chosen from the whole of the area; 20% of the addresses were chosen specifically from more deprived areas. A map showing the 6000 addresses is here:

The invitation included the following summary card (as well as a letter and FAQ):


All participants in the Ideas Exchange will receive up to £400 in recognition of the considerable time and energy that the process requires of them. Invitations were open for two weeks and at the end of this time 120 people had registered their interest in taking part.

Stage 2

As part of the sign-up procedure, all potential participants were required to share some basic information about themselves. We asked them to share their address, their date of birth, their sex and their ethnicity. We also asked if they describe themselves as having a disability.

We then used this information as input into a "sortition algorithm"; this is a process of randomly selecting our 18 Ideas Exchange members from the pool of 120 potential members in such a way that we have a representative sample (so, for instance, the age profile of Ideas Exchange members is broadly similar to the age profile of the population as a whole). The algorithm that we use is the fairest possible.

In addition to the information about sex, age, ethnicity and disability mentioned above, we also used the address of each respondent to hit one further target:

  • Index of multiple deprivation (IMD): We used government statistics that classify how deprived different areas of the country are (with 1 being most deprived and 10 being least deprived). Our sortition algorithm ensured, again, that the IMD profile in the Ideas Exchange reflected the IMD profile of the population as a whole.

Details of the selection process for this Ideas Exchange are summarised using the following pie charts, with further information following.

The way to understand these pie charts is as follows:

  • Column 1 (Target): These pie charts give information about the population as a whole, using various publicly available statistics (for instance via the ONS).
  • Column 2 (Respondents): These pie charts summarise the information that was provided to us by the 120 people who signed up as potential participants. There is some skewing in statistics here compared with our target: for instance, notice that a higher proportion of 30-44 year olds signed up to participate as compared to what we might expect in the population. 
  • Column 3 ( Confirmed Selected): These pie charts summarise information about the 18 people who were finally confirmed to participate in the Ideas Exchange. Notice that, thanks to our use of a sortition algorithm, the pie charts in this column are very similar to the target charts in the first column. As part of our recruitment process all of these people were contacted by telephone to confirm that they were still willing and able to participate -- in the event that this was not the case, we used the sortition algorithm to replace people who dropped out with others who shared similar characteristics.

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