> Was Yang planning to exempt any part of the GDP from his VAT?

A lot of GDP is exempt from VAT by design. It's easiest to see if you look at the expenditure approach to GDP. For a simplest example, government expenditure is effectively exempt from VAT. Exports are VAT-exempt (though it only matters if you export more than import, because imports are subtracted in expenditure approach to GDP calculation). Another part of GDP effectively exempt from VAT is capital goods: when a business buys a piece of equipment, it technically pays VAT on it, but it also gets the same amount they paid as a credit for the VAT due on their own sales. The business gets to "consume" the capital good by utilizing it in production process, but doesn't pay any VAT for it on net.