What is Sunset Industry?

Legal Definition
A sunset industry is an industry in decline, one that has passed its peak or boom periods. As one example, analogue recording technologies for audio or video have been supplanted by digital equivalents; although analogue equipment is still offered, sales have declined dramatically and are not expected to recover, so this segment of the market has been branded a 'sunset industry'.
-- Wikipedia
Legal Definition
An older and still important industry slowly losing investor favor due to falling capacity for generating employment and profits.