pre_text: Net Debt to Adjusted EBITDA Ratio (UNAUDITED) ($ in millions) (1) 2017 Adjusted EBITDA shown pro forma, assuming the Level 3 acquisition and the colocation and data center sale took place on January 1, 2017.
table: 2019 2018 2017(1)
table: Gross Debt $35,039 36,352 38,053
table: Cash and cash equivalents (1,690) (488) (551)
table: Net debt $33,349 35,864 37,502
table: Adjusted EBITDA excluding integration and transformation costs and special items (1) $9,070 9,040 8,686
table: Net Debt to Adjusted EBITDA Ratio 3.7 4.0 4.3
question: Analyse this data from a financial earnings document. What is the change in gross debt in 2019 from 2018?