Objective: To evaluate the effectiveness of taxes on unhealthy foods and subsidies for healthy foods in modifying the purchasing and consumption behavior of people in the Metropolitan Region, Chile.

Research hypothesis:

1. The application of a tax that increases the price of "High in" foods by 20% will reduce the purchase and consumption of these foods by 24%.
2. The application of a subsidy that reduces the price of fruits and vegetables by 20% will increase the purchase and consumption of these foods by 17%.
3. People of lower socioeconomic status are more sensitive to price changes than people of higher socioeconomic status.

Methodological design. The research proposal proposes an experimental design that will select the participants from a panel composed of people over 18 years of age, men and women, and of all socioeconomic levels. The methodological design considers a random assignment of the people eligible for the study into 3 groups:

1. First group of intervention (GI1): people who will make their purchases with taxes on food and beverages "High in";
2. Second intervention group (GI2): people who will make their purchases with subsidies for fruits and vegetables;

4. Control group (CG) that will make the purchases with the market prices or currently applied by the supermarkets or purchase scenarios.

Methodology. Participants will make a monthly simulated purchase through a simulated supermarket system with products similar to those found in real supermarkets, including "High in" products and fruits and vegetables. Different prices will be applied to each group depending on the type of food. With the data of simulated purchases, a variation of the demand and by socioeconomic subgroup will be calculated. The results will be compared with the control group.

Expected results. GI1 participants are expected to modify their purchase intention with the "High in" food tax, decreasing the purchase of these products in their simulated purchases, compared to CG participants who will make their simulated purchases without taxes. Likewise, IG2 participants are expected to modify their purchase intention with the fruit and vegetable subsidy, increasing the purchase of these foods, compared to CG participants. Finally, it is assumed that the reduction in simulated purchases of "High in" foods and the increase in simulated purchases of fruits and vegetables vary according to socioeconomic level.

Inclusion Criteria:

• Over 18 years of age.
• Person responsible for household purchases.
• Living in a household with one or more boys or girls between 2-14 years of age

Exclusion Criteria:

• That in the home there are no dietary restrictions that prevent the development of this research such as eating disorders, food allergies

It has not been decided yet. However, the project corresponds to a project awarded from public funds. So Fonis will also safeguard the information.

The results will be published and any information on the project may be requested in a general email from the School of Public Health of the Universidad Mayor (salud.publica@umayor.cl)

The participants were masked to the nature of the price sets to which they were assigned (although they were obviously exposed to the prices in the virtual supermarket). They were informed in the informed consent that the study was to evaluate fiscal policies.