Economists describe environmental impacts as negative externalities. Much environmental economics concerns externalities or "public bads". This distinction is essential when it comes to resolving inefficiencies that are caused by externalities. Market failures often exist in the form of externalities and natural monopolies. Examples of government regulation include privatization, regulation, and internalizing the externalities. Classic examples of externalities include pollution or overfishing. One of the public sector remedies for internalizing externalities is a corrective tax. In an equilibrium state, markets creating negative externalities of production will overproduce that good. These include environmental externalities or grid upgrades requirements. In an equilibrium state, markets creating positive externalities of production will underproduce their good. This incentivizes agents to consume them without paying the full cost, leading to negative externalities. For these reasons, negative externalities are more problematic than positive externalities. It incorporates all negative and positive externalities, of both production and consumption. This idea influenced Marshall's pupil Arthur Pigou's ideas on taxing negative externalities. Economists refer to these patterns as "externalities".