old_contents: nlcd_years = [2001, 2006, 2011]
  
  values = {'11': 'Open Water',
            '12': 'Perennial Ice/Snow',
            '21': 'Developed, Open Space',
            '22': 'Developed, Low Intensity',
            '23': 'Developed, Medium Intensity',
            '24': 'Developed High Intensity',
            '31': 'Barren Land (Rock/Sand/Clay)',
            '41': 'Deciduous Forest',
            '42': 'Evergreen Forest',
            '43': 'Mixed Forest',
            '51': 'Dwarf Scrub',
            '52': 'Shrub/Scrub',
            '71': 'Grassland/Herbaceous',
            '72': 'Sedge/Herbaceous',
            '73': 'Lichens',
            '74': 'Moss',
            '81': 'Pasture/Hay',
            '82': 'Cultivated Crops',
            '90': 'Woody Wetlands',
            '95': 'Emergent Herbaceous Wetlands'
            }
  
  categories = {'Water': ('11', '12'),
                'Developed': ('21', '22', '23', '24'),
                'Barren': ('31',),
                'Forest': ('41', '42', '43'),
                'Shrubland': ('51', '52'),
                'Herbaceous': ('71', '72', '73', '74'),
                'Planted': ('81', '82'),
                'Wetlands': ('90', '95')
                }
  
  
new_contents: nlcd_years = [1992, 2001, 2006, 2011]
  
  values = {'11': 'Open Water',
            '12': 'Perennial Ice/Snow',
            '21': 'Developed, Open Space',
            '22': 'Developed, Low Intensity',
            '23': 'Developed, Medium Intensity',
            '24': 'Developed High Intensity',
            '31': 'Barren Land (Rock/Sand/Clay)',
            '41': 'Deciduous Forest',
            '42': 'Evergreen Forest',
            '43': 'Mixed Forest',
            '51': 'Dwarf Scrub',
            '52': 'Shrub/Scrub',
            '71': 'Grassland/Herbaceous',
            '72': 'Sedge/Herbaceous',
            '73': 'Lichens',
            '74': 'Moss',
            '81': 'Pasture/Hay',
            '82': 'Cultivated Crops',
            '90': 'Woody Wetlands',
            '95': 'Emergent Herbaceous Wetlands'
            }
  
  categories = {'Water': ('11', '12'),
                'Developed': ('21', '22', '23', '24'),
                'Barren': ('31',),
                'Forest': ('41', '42', '43'),
                'Shrubland': ('51', '52'),
                'Herbaceous': ('71', '72', '73', '74'),
                'Planted': ('81', '82'),
                'Wetlands': ('90', '95')
                }
  
  categories_change_1992 = {'Water': (1, 12, 13, 14, 15, 16, 17, 18),
                            'Urban': (2, 21, 23, 24, 25, 26, 27, 28),
                            'Barren': (3, 31, 32, 34, 35, 36, 37, 38),
                            'Forest': (4, 41, 42, 43, 45, 46, 47, 48),
                            'Shrubland': (5, 51, 52, 53, 54, 56, 57, 58),
                            'Agriculture': (6, 61, 62, 63, 64, 65, 67, 68),
                            'Wetlands': (7, 71, 72, 73, 74, 75, 76),
                            }
  
  
subject: Add 1992 years