Self-response in the 2020 Census included several major differences relative to the 2010 Census, including: (1) an internet response option that allowed for response with or without a unique Census ID, (2) tailored mail contact strategies in which different geographic areas received different mail materials for a total of up to seven mailings, (3) a telephone number for Census Questionnaire Assistance (CQA) available on all mailings that allowed callers to provide their census data by phone, (4) responses in multiple modes, using multiple device types, and in multiple languages, (5) an integrated partnership and communications program that featured local and national partnerships and microtargeted advertising to promote self-response, and (6) instead of delivering the mailings to the whole country on a single day, each of the mailings were stretched out over a one-week period into groups of four different mail cohorts. These response features were a part of the innovation area called Optimizing Self-Response (OSR) for the 2020 Census, and they primarily applied to the Type of Enumeration Area (TEA) called “Self-Response.” Other TEAs were contacted and enumerated but were out of the scope of this experiment.

This experiment sought to understand the net impacts of the OSR innovation area in the 2020 Census. In particular, the focus was to evaluate the quantitative impacts of the mailing strategy, the overall influence of the internet response option, and the impact of the communications campaign on internet and phone response. Therefore, the following experimental treatments were tested (strategies discussed in further detail in the next section):

• A sample of housing units received the 2010 Census mail strategy.
• A sample of housing units received the 2020 Census mail strategy with no mention of the option to respond using the internet.
• A sample of housing units had their mail contact strategy switched between Internet Choice and Internet First.
• A sample of housing units received no direct mailings from the Census Bureau.