Monetary and Non-Monetary Barriers to Accessing Environmental Public Benefit Programs: Experimental Evidence from California

This study will distribute a small number of portable residential air purifiers to residents in California. We sample a subset of California addresses and send an offer letter to purchase air purifiers at a discount. In the offer letter, we randomize the subsidy rate, the ordeal cost of application, and the amount of information pertaining to air quality and mitigation strategies. We will observe whether each letter recipient applies to the program through our online application portal. The following list summarizes the features of the treatment arms.

• T0: “Control” arm. The letter will encourage recipients to apply for an air purifier through our website. They will not be offered a subsidy, except for free shipping.
• T1: 50% subsidy treatment. The letter will encourage recipients to apply through our website for a 50% discount on an air purifier, plus free shipping.
• T2: 95% subsidy treatment. The letter will encourage recipients to apply through our website for a 95% discount on an air purifier, plus free shipping.
• T3: 100% subsidy treatment. The letter will encourage recipients to apply through our website for a free (100% discount) air purifier, plus free shipping.
• T4: 100% subsidy treatment with time costs. The letter will encourage recipients to apply through our website for a free air purifier. Applicants will be asked to fill out a longer form on the application portal that we expect to take approximately 15 minutes, as opposed to 5 minutes in other treatment arms.
• T5: 100% subsidy treatment with proof of residence. The letter will encourage recipients to apply through our website for a free air purifier. Applicants will be asked to upload a proof of residence, such as a bill delivered to them with their name and address on it. The treatment is otherwise identical to T3.
• T6: 100% subsidy treatment with proof of residence, access to a helpline, and information about the application process. The process is identical to T5, except for the following. First, the letter includes additional details about the types of forms that are required as proof of residence. Second, the letter also contains a phone number and an email address for additional assistance or questions, i.e., a helpline.
• T7: 100% subsidy treatment with information about air quality. The letter will encourage recipients to apply through our website for a free air purifier. They also receive additional information about the health impact of air pollution, summary statistics on poor air quality days in California overall and for their county based on the U.S. EPA AQI Report, and a link on our website for additional information about the health impact of air pollution and mitigation strategies.

2026-01-15

2027-01-15

- Applying (binary). This is a binary variable that is 1 if a letter recipient provides all required information and clicks “submit” on the
application form described in Section 2.5 and zero otherwise.
- Income (continuous). Self-reported annual household income of the applicant from 2024. The measure is collected as part of the application questionnaire.

N/A

- Started applying (binary). 1 if the recipient starts the application form by typing in their personal code and clicking “next,” and zero otherwise. This measure captures the first instance in which we capture the recipient’s intent to apply, while they have not yet fully incurred the opportunity costs, such as filling the rest of the form or providing proof of residence.

- Ordered an air purifier (binary). 1 if the recipient orders a free or subsidized air purifier after applying for it and being selected as a winner, and zero otherwise. This measure captures the rate at which the letter recipient takes up the air purifier, including payment and additional non- pecuniary costs of ordering the unit from the supplier. This would only be observable on the subset of applicants selected through a random draft.

- High income (binary). 1 if the household’s estimated income is higher than $75,000, and 0 otherwise and non-missing, based on the binned estimates from the mailer data.

The sampling frame is based on a mailing list purchased from a direct mailing company, containing approximately 12 million individuals from the State of California. We stratify the restricted mailing list based on the estimated income, household size, and county-level PM2.5 concentration. We use the mailing list's binned measure for estimated income. We group the household size into 1, 2, 3, and 4 or larger. We aggregate the PM2.5 measures into quartiles at the county level. The strata are interactions of the income, household, and PM2.5 bins. We sample 120,000 addresses from the stratified list, with twice as large a sampling probability for strata with household income less than $75,000. We employ differential weights so that the program targets lower-income households, as per the policy objective of our subsidized air purifier program.

We assign each of the 120,000 sampled addresses to eight groups via stratified randomization. We use the same stratification procedure as in sampling. The treatment arms receive an equal number of addresses.

Not available

Randomization done in office by a computer (Stata)

Individual

No

N/A

120,000 households

15,000 letters to each of 8 treatment arms

For the binary application outcome, we calculate the minimum detectable treatment effect sizes based on the linear probability model. Our prior on the baseline response rate is somewhere around 2 to 3 percent with a “standard” offer, i.e., either no subsidy (T0) or lower subsidy (T1) with no additional information or non-pecuniary costs. The MDEs in levels are around 0.2 to 0.8 percentage points for the baseline response rates of 0.25 to 5%. Because of the large sample size, the MDEs are small relative to the standard deviation: the MDEs are 0.036SD with Bonferroni corrections (with two hypotheses) and 0.032SD without. The MDEs are somewhat large compared to the baseline response rates; they can be as large as 25% of the baseline rate of 0.25% and as small as 14% of the baseline rate of 5%.