This report is the first in a series aimed at providing a comprehensive understanding of employee engagement and happiness in the workplace using the HF 2021 Employee Engagement Dataset. It focuses on evaluating data quality and reliability, assessing the construct validity of survey measures, identifying key drivers of workplace happiness, exploring group differences, and modeling changes in employee happiness over time. Key highlights include addressing inconsistencies in gender labels, missing data, and improbable dates to ensure robust analyses; observing significant variations in happiness levels by age group, particularly during the COVID-19 pandemic; and identifying company-level differences in average happiness scores, which emphasize the role of organizational culture in shaping well-being. By establishing a foundation of clean, well-prepared data and understanding its structure, this report empowers organizations to better understand their workforce, implement targeted strategies to enhance engagement, and foster more positive and productive workplaces.