Understanding The Hand Method
A Gini index measures inequality inside a set of nonnegative values. A score near zero means the values are very even. A score near one means one person, item, or group holds most of the total. This page builds the same table you would build on paper.
The first step is sorting. Values must move from smallest to largest. Each value may also have a weight. A weight can represent people, households, claims, stores, or repeated records. If no weight is entered, every row receives a weight of one.
Building The Lorenz Table
The calculator multiplies each value by its weight. It then finds cumulative weight and cumulative weighted value. These totals are divided by the grand totals. That creates cumulative population share and cumulative value share. These two shares form Lorenz curve points.
The Gini index comes from the area between perfect equality and the Lorenz curve. The tool uses trapezoids between each pair of Lorenz points. Each row shows the double area term used in the final subtraction. This makes the answer easy to verify by hand.
Why This Calculator Helps
Manual Gini work can become slow when datasets have many rows. Small rounding errors also change the final value. This calculator keeps the steps visible. You can compare the Lorenz result with an unweighted rank formula when weights are not used. You can also apply a small sample correction when a corrected score is needed.
Practical Uses
The Gini index is common in income studies, market share reviews, risk scoring, model checks, and resource allocation. It can compare areas, customer groups, departments, or product categories. It should not be read alone. Always check the original values, sample size, weights, and context. Two datasets can share the same Gini score while having very different shapes.
Good Input Habits
Use clean numeric values. Keep all values nonnegative. Put weights in the same order as the values. Do not use percentages as weights unless they describe record counts or shares. After calculating, review the sorted table. Then export the CSV or PDF for notes, lessons, audits, or reports. Save the method used too. That helps readers quickly understand assumptions behind the final number during later reviews.