The Corvette vessel type was born during the "Age of Sail". Modern Corvettes are typically dimensionally smaller than Frigates and larger than Coastal Patrol Craft though the differences between Frigates and Corvettes begins to lessen when some navies consider certain vessels Corvettes when they could technically be described as Frigates. Corvettes supply a balanced mix of firepower, ocean-going capabilities and rotary-wing support while presenting reasonable economic benefits. Not every major naval power emphasizes the Corvette as part of its surface fleet - though they are consistently found in numerically smaller navies of the world.
For the purposes of the GFP final ranking, landlocked nations are not penalized for the lack of a standing naval force. However, nations with a standing navy ARE penalized for lack of certain naval assets.
Corvette strength data through 2016.
Sources: CIA.gov, CIA World Factbook, wikipedia.com, public domain print and media sources and user contributions. Some values may be estimated when official sources are lacking.