None listed
Conditions
Brief summary
The aim of this research is: 1) to derive accurate and more precise food price elasticity (PE) values; 2) to quantify the impact of price changes on quantity and quality of discrete food groups and; 3) to model the potential health and disease impacts of these food pricing policy options. This study combines experimental and simulation modelling methods using four steps, including: econometrics (step 1); experimental methods (step 2); economic modelling (step 3); and simulation modelling (step 4). This trial registry focuses on the experimental phase. This experiment is not a traditional RCT testing intervention control, but is designed to measure multiple responses to changing food prices that can feed into simulation models to estimate more precise price elasticity values. For the experimental phase, we aim to randomize N=1,000 adults from the general NZ population and ask them to complete five weekly shops for their household in a New Zealand Virtual Supermarket for five consecutive weeks. The Virtual Supermarket includes around 1400 unique food and beverage items. Participants can complete this study from home. This study is experimental and people will pay with virtual money. Real groceries will not be provided. During the virtual shopping tasks, participants will be exposed to random varying sets of food prices in the Virtual Supermarket. The price sets will be constructed in the simulation modelling phase that occurs prior to this experimental phase. In total, we will construct 5,100 different price sets (1,000 participants * 5 shops + 100 back up) and each study participant will be exposed to a different price set during each of their five virtual shops. The price sets will be divided into five categories in line with five pre-determined fiscal policy options (sugar tax, saturated fat tax, salt tax, sugar sweetened beverage tax and fruit and vegetable subsidy). This means that we will have around 1,000 different price sets per policy option (e.g., 1,000 price sets for a soft drink tax, 1,000 price sets for a fruit and vegetable subsidy, etc.). Within each price set, the price of all products will vary, but we will simulate larger price variations for particular products depending on the policy option of interest (for example, we will have more variation in soft drink prices for the soft drink tax scenario). Data from this experiment will then be put into econometric models to derive more accurate food price elasticity values which will subsequently feed into macro-simulation models to quantify the impact of price changes on quantity and quality of food choices and to model the potential health and disease impacts of these policy options.
Interventions
Price ExaM combines experimental, economic and simulation modelling methods to derive more accurate and precise food price elasticity values (e.g., change in demand in response to change in price). These values are needed to design better policy advise on health-related food taxes and subsidies. The study contains four steps, including: econometrics (step 1); experimental methods (step 2); economic modelling (step 3); and simulation modelling (step 4). This trial registration covers step 2.
T
Price ExaM combines experimental, economic and simulation modelling methods to derive more accurate and precise food price elasticity values (e.g., change in demand in response to change in price). These values are needed to design better policy advise on health-related food taxes and subsidies. The study contains four steps, including: econometrics (step 1); experimental methods (step 2); economic modelling (step 3); and simulation modelling (step 4). This trial registration covers step 2. The experimental phase is not a traditional RCT testing intervention versus control. Instead, the experimental phase is designed to obtain results that can feed into the subsequent modelling phases. During the experimental phase, we will expose study participants to randomly changing food prices (different price sets). We will use our Virtual Supermarket and ask 1,000 participants to complete five household food shops over five consecutive weeks. The Virtual Supermarket is a three-dimensional computer simulation of a real New Zealand supermarket. The Virtual Supermarket has a product selection that is representative for an average NZ supermarket and includes 1450 unique food and beverage products. Participants can navigate a shopping trolley in this virtual tool and select products from the shelves with a mouse click. Prices are clearly marked on the shelve. Participants complete the entire study online, using our Price ExaM website containing all forms (registration, consent, questionnaires) the Virtual Supermarket software and instruction material (including manuals and videos). Following registration and consent, participants are able to download the Virtual Supermarket on their computer. Next, they login with their registration number. At their first login, participants are asked to complete a tutorial where they have to find and purchase six products in the Virtual Supermarket. This tutorial helps participants to become familiar with the software. After completing the tutorial, participants can start their first shop where they will be randomized to a different price set each time they shop (see below). In the econometric phase (prior to the experimental phase), we design price sets with varying prices for all 1450 products in the Virtual Supermarket. Participants will be exposed to these prices within the Virtual Supermarket. These price sets are designed using econometric methods in a way that allows us to maximise the precision of price elasticities across individuals and within individuals estimated from the subsequent steps in the study. We develop different price sets for each participant and for each virtual shop, meaning that we will have 5,100 price sets in total (1000 participants * 5 shops + 100 back-up price sets). The price sets will be divided into five broad categories in line with five policy options (sugar tax, saturated fat tax, salt tax, sugar-sweetened beverage (SSB) tax and fruit and vegetable subsidy). Within each price set, the price of all products will vary (baseline variation), and we will add the taxes/subsidies on top of these price sets leading to larger price variations for particular products depending on the particular policy option (for example, we will have more variations in SSB prices in SSB tax scenario). 15% of the price sets will not receive a tax / subsidy (e.g., will only have baseline variation). Using this approach, Price ExaM will provide precise price elasticity data for any food group which can be used to test any food tax, but will maximise precision about PE values for the five most likely policy options. Participants will be randomly assigned to one of the 5,100 price sets each time they shop (e.g., participants can receive any of the 5,100 price sets). The price sets are allocated from our price set database using a random generator, with the only restriction being that a price set cannot be used more than once. Participants do not necessarily receive price sets within the same policy option for each shop and randomization is not stratified (i.e., it is completely random). The Virtual Supermarket collects all purchased products and their prices. Participants’ virtual purchase responses will then feed into the next economic modelling phase. Participants are informed that this study aims to measure shopping behaviour. Participants are also informed that prices in the Virtual Supermarket vary and they are able to see the prices when they shop. However participants are not informed: (i) how the prices vary; (ii) how these price changes relate to fiscal policy options; (iii) and how the study relates to health outcomes. Participants can complete the study using any computer or laptop. Each shop takes around 30 minutes to complete and there is not time limit to complete the shop.
Sponsors
Dr Wilma Waterlander
Study design
Allocation
Randomised controlled trial
Intervention model
Other
Primary purpose
Prevention
Masking
Blinded (masking used) (Subject, Caregiver, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
All
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
-Adults (18 years or over) -Contributes to household grocery shopping -Speaks and reads English -Has access to a computer and internet and able to download the software onto that computer (tablets and smartphones are not compatible with the Virtual Supermarket software). -Has an email address (provided at screening stage) -Able to use basic functions of a computer such as opening the internet browser, using email and saving files. -Available to conduct five consecutive weekly shops in the Virtual Supermarket during the required study period.
Exclusion criteria
Another person in the same household already participating in the study.
Outcome results
None listed