A permanent decline in the market value of an asset is called

Impairment

Explanation:

When an asset's market price is lower than what is reported in the financial statements, it is referred to as an impaired asset. It is reduction in the market value of a fixed tangible or intangible asset permanently.

Such assets does not yield positive cash flow in future. If an asset is identified as impaired, then loss related to it, also called impairment loss should be recorded in the income statement.