Why do we think that dark matter exists?​

To explain the unexplained motions of the stars in the galaxies.

Explanation:

Scientists study dark matter by looking at the effects it has on visible objects. Scientists believe that dark matter may account for the unexplained motions of stars within galaxies. ... They allow scientists to create models which predict galaxy behavior. Satellites are also being used to gather dark matterinformation.

disequilibrium means that either supply is greater than the demand for an available good, or that the demand for a product outstrips the available supply. it implies that the price for a is either too low creating large demand, or too high creating a large surplus of supply.