tax - on a per-unit basis, cost divided between consumer and producer  

• subsidy - essentially a negative tax
• treated as an increased cost, this will lead to lower consumption/production

• p_b = price that consumers pay
• p_s = price that producers receive
• p_b - p_s = tax
• gov't revenue = A+B
• deadweight loss = C+D
• consumer surplus decreases by A+C
• producer surplus decreases by B+D

subsidies - moves to the other side of the graph (scandalous!)  

• p_s - p_b = subsidy
• note that the p_s and p_b have switched locations from before
• costs the gov't A+B+C+D+E+F
• consumer surplus increases by D+E
• producer surplus increases by A+B
• net deadweight welfare loss of C+F