What is vertical fiscal imbalance?

The role of the 16th Finance Commission should be to eliminate vertical fiscal imbalance in federal relations. What should it do when revenues are concentrated with the Union government, and the States are burdened with expenditure responsibilities?

What is vertical fiscal imbalance?
The role of the 16th Finance Commission should be to eliminate vertical fiscal imbalance in federal relations. What should it do when revenues are concentrated with the Union government, and the States are burdened with expenditure responsibilities?