pre_text: Net Cash Provided By Operating Activities and Free Cash Flow The following table presents a reconciliation of net cash provided by operating activities to free cash flow (in thousands, except for percentages): Net cash provided by operating activities for the twelve months ended December 31, 2019 was $115.5 million as compared to $90.3 million during the same period in 2018. The increase was primarily due to improved profitability, improved collections, and other working capital changes in 2019 when compared to the same period in 2018. Free cash flow for the twelve months ended December 31, 2019 was $72.8 million, resulting in a free cash flow margin of 12.6%, as compared to free cash flow of $49.8 million and a free cash flow margin of 9.3% for the same period in 2018. The increase was primarily due to both improved profitability and collections, and is partially offset by cash paid for interest on our convertible notes of $17.4 million in the twelve months ended December 31, 2019. Refer to the section titled “Liquidity and Capital Resources” for additional information on the convertible notes.
table: Year Ended December 31,
table: 2019 2018 2017
table: Reconciliation of free cash flow:
table: Net cash provided by operating activities $115,549 $90,253 $67,510
table: Capital expenditures (18,034) (14,895) (7,100)
table: Capitalized software costs (24,668) (25,515) (20,571)
table: Free cash flow $72,847 $49,843 $39,839
table: Free cash flow margin 12.6% 9.3% 8.3%
question: Analyse this data from a financial earnings document. What was the change in free cash flow between 2018 and 2019?