The rule of taxation shall be uniform but the legislature may empower cities, villages or towns to collect and return taxes on real estate located therein by optional methods. Taxes shall be levied upon such property with such classifications as to forests and minerals including or separate or severed from the land, as the legislature shall prescribe. Taxation of agricultural land and undeveloped land, both as defined by law, need not be uniform with the taxation of each other nor with the taxation of other real property. Taxation of merchants’ stock−in−trade, manufacturers’ materials and finished products, and livestock need not be uniform
with the taxation of real property and other personal property, but the taxation of all such merchants’ stock−in−trade, manufacturers’ materials and finished products and livestock shall be uniform, except that the legislature may provide that the value thereof shall be determined on an average basis. Taxes may also be imposed on incomes, privileges and occupations, which taxesmay be graduated and progressive, and reasonable exemptions may be provided.