Net Value Added at Market Price (NVA$_{MP}$) is derived by adjusting Gross Value Added at Market Price (GVA$_{MP}$) for net indirect taxes. Specifically, net indirect taxes (calculated as taxes less subsidies) are added to GVA$_{MP}$ to determine NVA$_{MP}$, as these taxes represent an element of economic value that influences the final market price of goods and services.