Effective demand for a commodity is desire for that commodity backed by_______

A commodity is defined as normal when its demand changes in the same direction as______

Which of the following matters may account for changes in demand?
 

I - changes in consumer preferences
II - changes in real income
III - changes in distribution of incomes
IV - changes in levels of taxation

An example of a market which approaches fairly near to perfection is____________

Whether a monopolist is able to increase his revenue by restricting his output depends on the shape of the_________