pre_text: AMERICAN TOWER CORPORATION AND SUBSIDIARIES SCHEDULE III—SCHEDULE OF REAL ESTATE AND ACCUMULATED DEPRECIATION (dollars in millions) (7) Primarily includes foreign currency exchange rate fluctuations and other deductions.
table: 2019 2018 2017
table: Gross amount of accumulated depreciation at beginning $(5,724.7) $(5,181.2) $(4,548.1)
table: Additions during period:
table: Depreciation (768.4) (751.4) (718.7)
table: Other — — —
table: Total additions (768.4) (751.4) (718.7)
table: Deductions during period:
table: Amount of accumulated depreciation for assets sold or disposed 121.4 129.3 100.7
table: Other (7) (10.5) 78.6 (15.1)
table: Total deductions 110.9 207.9 85.6
table: Balance at end $(6,382.2) $(5,724.7) $(5,181.2)
question: Analyse this data from a financial earnings document. What was the change in Gross amount of accumulated depreciation at beginning between 2017 and 2018?