A weighted average of national, state and local Gini coefficient rates would incentivize local employers to raise wages. Walmart and Costco paying $15/hr everywhere would drive your local Gini down too. You, local HNW or UHNW person, would be incentivized to raise your employees' wages to lower your local Gini and cut your tax rate. If you're an asset manager employing only 11 people in lower Gini than SF or NY Omaha, you might even get an undeserving tax rate cut or smaller tax rate increase than your SF or NY counterparts. But you'd be incentivized to lobby your investee companies to raise wages nationally. Gini tax indexation sets up a Keynesian-type virtuous circle of higher wages generating higher demand and incentivizing employers to invest in labor-saving tech that raises productivity instead of sticking to cheap labor business models. Look at the Norwegian car wash vs the American car wash example in The Economics of Belonging, Martin Sandbu. Increasing labor's bargaining power is good for all of us.