Does bottle size and glass size influence how much wine people drink at home?

INTERVENTION: General population households will be exposed to two interventions comprising i) two different bottles sizes (within‐subjects factor), randomized in their order of presentation and separated by a ‘usual behaviour’ period, and ii) one of two different glass sizes (between‐subjects factor). Bottle size The two conditions comprise purchasing a given quantity of wine, sub‐divided into bottles of one of two different sizes: 1. 75 cl 2. 37.5 cl Each of the two intervention periods will last two weeks (14 days), with an intervening ‘usual behaviour’ period of a maximum of three weeks, with exact duration determined by how long it takes each household to finish the wine ordered during the first intervention period. During each of two 14‐day intervention periods, participants will be requested to purchase online three weeks’ worth of wine (based on their self‐reported baseline consumption) in their allocated bottle size. The total volume of wine purchased will be the same across both intervention periods. In order to confirm they have ordered the appropriate wines (amount and size), participants will be requested to send a copy of the order to the research team. Glass size Households will also be randomised to receive either: 1. Small glasses (290 ml) or 2. Large glasses (350 ml) glasses Wine purchased for the study will be drunk in one of two possible glass sizes. Both sizes of glass will be of the same design (Royal Leerdam Bouquet). Households will receive a set of glasses through the post – with the exact number depending on the number of wine drinkers within a household – to use wh CONDITION: Alcohol consumption ; Not Applicable SECONDARY OUTCOME: ; The mean number of days taken to consume each 1.5 litres of wine during each intervention period with each bottle‐glass size combination, estimated from the start and finish dates reported on submitted photographs.; ; Secondary analysis; Regression analysis will be used to predict the time taken (in days) to consume each unit of 1.5 litres of wine from each bottle size with each glass size. Analyses will control for all specified covariates.; ; Measurements will be conducted on Day 7 and Day 14 of the first intervention period (i.e. 1 week and 2 weeks after the beginning of the study), as well as on Day 7 and Day 14 of the second intervention period (i.e. 3 weeks and 4 weeks after the beginning of the study; or 4 weeks and 5 weeks after the beginning of the study; or 5 weeks and 6 weeks after the beginning of the study or 6 weeks and 7 weeks after the beginning of the study, depending on the duration of the ‘usual behaviour’ period which will last a maximum of 3 weeks).; PRIMARY OUTCOME: ; Volume of study wine consumed (in millilitres) during each intervention period for each bottle‐glass size combination, estimated through returned photographs of all study wine bottles purchased.; ; Amounts consumed from opened bottles will be estimated from photographs of the bottles being weighted on provided study scales. Estimates will be based on the following procedures:; 1. Three of each of the bottles on the study wine list (i.e. 66 bottles: 33 x 75 cl and 33 x 37.5 cl bottles) will be weighed when full in advance of the study commencing. Any variations in the amount of liquid in the bottles of the same wine or the weight of the empty bottle will be reported, and the average value will be used in all study calculations.; 2. The weight of 1cl of wine will be estimated and used to calculate the weight of the wine in any partially full bottle of either size.; 3. The observed weight of the partially full bottle will be subtracted from the weight of the full bottle to give an estimate of the weight of the consumed wine.; 4. The validity of the assumptions informing steps 1‐3 above will be checked using four selected wines (those with the highest and lowest ABV) in each of 75 cl and 37.5 cl bottle sizes, weighing both full and empty bottles.; ; Primary analysis; Regression analysis will be used to predict wine consumption (in ml) at 14 days from each bottle size with each glass size. Analyses will control for the following covariates:; 1. In‐home consumption of non‐study wine (in millilitres) by the household during each of the two 14‐day intervention periods, assessed by self‐reports on bottle labels; 2. Use of non‐study wine glasses assessed by photographs and self‐report; 3. Guest consumption of study wine (in millilitres) during each of the two 14‐day intervention periods, assessed by self‐reports on bottle labels; 4. Out‐of‐home consumption (in millilitres) by household members during each intervention period, assessed by self‐report; 5. Amount of other alcohol (non‐wine) consumed (in millilitre) by household members in and outside the home, during each intervention period, assessed by self‐report; 6. Number of wine drinkers in the household; 7. Duration (in days) of ‘usual behaviour’ period; 8. Baseline consumption (in millilitres) of wine per week, self‐reported; 9. Price per litre of all ordered wine; 10. Awareness of study aim, assessed in the end‐of‐study self‐report questionnaire; 11. Mitigating factors i.e. any noteworthy events or circumstances external to the study, self‐reported as having increased or decreased wine consumption during each intervention period; ; Measurements will be conducted on Day 7 and Day 14 of the first intervention period (i.e. 1 week and 2 weeks after the beginning of the study), as well as on Day 7 and Day 14 of the second intervention period (i.e. 3 weeks and 4 weeks after the beginning of the study; or 4 weeks and 5 weeks after the beginning of the study; or 5 weeks and 6 weeks after the beginning of the study or 6 weeks and 7 weeks after the beginning of the study, depending on the duration of the ‘usual behaviour’ period which will last a maximum of 3 weeks).; INCLUSION CRITERIA: Eligible households are those in which adult members meet the following criteria: 1. Self‐report that they collectively drink at least 2 x 75 cl bottles of wine (1.5 litres) a week 2. Usually purchase wine online or are willing to purchase wine online 3. Are willing to consume wine(s) exclusively from the study wine list and order a total of approximately 6 weeks’ worth of wine 4. Be prepared to drink all study wine (including both red and white) from the study wine glasses 5. Are in possession of a smartphone or similar device from which to send photographs of wine bottles and wine glasses 6. Do not take medications for which there is a recommendation against alcohol consumption 7. Are not pregnant or are planning on becoming pregnant during the study period 8. Do not have a history of becoming i