Energy policy is the manner in which a given entity (often governmental) has decided to address issues of energy development including energy conversion, distribution and use. The attributes of energy policy may include legislation, international treaties, incentives to investment, guidelines for energy conservation, taxation and other public policy techniques. Energy is a core component of modern economies. A functioning economy requires not only labor and capital but also energy, for manufacturing processes, transportation, communication, agriculture, and more. Energy sources are measured in different physical units: liquid fuels in barrels or gallons, natural gas in cubic feet, coal in short tons, and electricity in kilowatts and kilowatthours.