Here I think it's useful to think about the externality of the demand shortfall.
From the economist.com
But it is possible that buying genuine luxuries imposes an externality of its own.
From the economist.com
But what if the externality could be accounted for, in a way that helped the poor?
From the time.com
Because the externality is so indirect, they come up with outlandish figures.
From the Economist.com
A Pigovian tax is a tax imposed that is equal in value to the negative externality.
From the en.wikipedia.org
Is the timescale effect not more significant in Pigovian terms than the externality?
From the economist.com
Land value is a positive externality of everyone else's economic activity.
From the economist.com
All charity is all externality for the giver but that doesn't stop charitable giving.
From the economist.com
An example of an externality is a factory that engages in water pollution in a river.
From the en.wikipedia.org
More examples
Outwardness: the quality or state of being outside or directed toward or relating to the outside or exterior; "the outwardness of the world"
In economics, an externality (or transaction spillover) is a cost or benefit, not transmitted through prices , incurred by a party who did not agree to the action causing the cost or benefit. ...
The state of being external or externalized; A thing that is external relative to something else; An impact, positive or negative, on any party not involved in a given economic transaction or act
(externalities) An externality occurs in economics when a decision (for example, to pollute the atmosphere) causes costs or benefits to individuals or groups other than the person making the decision. ...
(Externalities) By-products of activities that affect the well-being of people or damage the environment, where those impacts are not reflected in market prices. The costs (or benefits) associated with externalities do not enter standard cost accounting schemes.
(Externalities (to higher education)) Economic benefits of higher education to society which are not captured by the additional average pay received by graduates (the pay premium ) and so reflected in the rate of return . See Report 8 for more information.
(Externalities) Costs that are not factored into ("internalized") electricity generation, such as the environmental costs of additional pollution
(Externalities) The consequences or impacts of resource decisions that are not directly accounted for in the price paid for the resource.
(Externalities) The genuine, but unpaid for financial, physical and environmental impacts of a business or a government activity (e.g. pesticide use). ...