The visualization, titled “Treasury,” presents a detailed breakdown of income distribution across New Zealand’s population, segmented by income tier, gender, ethnicity, and age group. The data, sourced from a gist, is rendered using D3 v3 with SVG and animation. The visualization uses a stacked bar or area chart layout where each income tier (No Income, <5000) is represented as a horizontal band, with the height of each segment proportional to the population count for that demographic combination. The `tierPos` column likely defines the starting y-position for each tier, and `tierh` sets the band height. Colors encode ethnicity, and within each band, segments are grouped by gender and ordered by age, allowing comparisons across demographic categories. Animated transitions highlight changes or re-sort the data, making it easy to explore how income distribution varies across age groups, genders, and ethnicities.