In the last chapter of Capitalism, Shaikh highlights a few areas for further research which real economic analysis can address, including development and underdevelopment, and rising inequality. Within that chapter, the subsection "Rising inequality and the class distribution of income" provides an equation for before-tax income inequality. Taking that as a starting point, I attempted to extend the analysis to evaluate after-tax income inequality and also wealth inequality (including deriving equations for after-tax income and wealth Gini indices and comparing against empirical data). This is of course a large topic which calls for further refinement and elaboration and so I am sharing my work here (see pdf; The Economic Basis of Social Polarization is also freely available on Google Books).
Here is a brief description of the work: The economic basis of social polarization is empirically evaluated in the US (from the post-World War II boom through neoliberalism) and comparisons are made with the rest of the G7 (under neoliberalism). Income inequality is explained in terms of three factors: the profit share of net value added, tax redistribution, and the proportion of profit distributed to households. Wealth inequality is explained in terms of two factors: the proportions of assets and liabilities comprising net wealth and the share of financial assets held by the ruling class. The division of net value added between wages and profit is further evaluated and explained in terms of fundamental factors shaping capitalist development: profitability, capital accumulation, capital intensity, and the wage rate.