Inflation and effective government cuts to the license fee.
BBC license fee in 2010 was £145.50, which is £233.72 in today's money.
The current license fee is £180. The license fee has risen well below inflation for years, and is £53.72 less than it should be. Thats an effective 23% cut in 16 years.
The BBC also had to take on the World Service budget from the foreign office, and provide free licenses to the elderly, plus other cost pressures.
This is what 14 years of Tory government got us, and Labour have no intention of increasing the license fee because any tax rises need to go elsewhere.