The purpose of this data guide is simple: to teach the skills of using data to make the case for investing in Head Start and Early Head Start to address the rising tide of need in your state. Used wisely, data can provide policymakers and community leaders the insight and information they need to make smarter investments in the success of every child. Here are some reasons why gathering data and using it effectively are so critically important: Data can inspire action. An organization, community or state may come together when they discover a gap or need; Data can help identify gaps in equity or access for different populations to understand the needs of the most marginalized and vulnerable children; Data can inform funding gaps and opportunities to leverage or layer funding to meet a need; Data provides a way to share evidence of progress with important stakeholders, including funders who want their investments to result in measurable and meaningful impacts; Each section of the guide explains why this stage is important and frames essential questions to consider. (author abstract)