Liquidity and Capital Resources
In assessing our short term and long term liquidity, management reviews and analyzes our current cash balances, short-term investments, accounts receivable, accounts payable, accrued liabilities, capital expenditure and operating expense commitments, and required finance lease, interest and debt payments and other obligations. In assessing our short term and long term liquidity, management reviews and analyzes our current cash balances, short-term investments, accounts receivable, accounts payable, accrued liabilities, capital expenditure and operating expense commitments, and required finance lease, interest and debt payments and other obligations.
The following table sets forth our consolidated cash flows.
Net Cash Provided By Operating Activities. Our primary source of operating cash is receipts from our customers who are billed on a monthly basis for our services. Our primary uses of operating cash are payments made to our vendors, employees and interest payments made to our finance lease vendors and our note holders. Our changes in cash provided by operating activities are primarily due to changes in our operating profit and changes in our interest payments. Cash provided by operating activities for 2019, 2018 and 2017 includes interest payments on our note obligations of $38.0 million, $32.7 million and $30.8 million, respectively.
Net Cash Used In Investing Activities. Our primary use of investing cash is for purchases of property and equipment. These amounts were $47.0 million, $49.9 million and $45.8 million for 2019, 2018 and 2017, respectively. The annual changes in purchases of property and equipment are primarily due to the timing and scope of our network expansion activities including geographic expansion and adding buildings to our network. In 2019, 2018 and 2017 we obtained $11.3 million, $9.9 million and $9.0 million, respectively, of network equipment and software in non-cash exchanges for notes payable under an installment payment agreement.
Net Cash Provided By (Used In) Financing Activities. Our primary uses of cash for financing activities are for dividend payments, stock purchases and principal payments under our finance lease obligations. Amounts paid under our stock buyback program were $6.6 million for 2018 and $1.8 million for 2017. There were no stock purchases for 2019. During 2019, 2018 and 2017 we paid $112.6 million, $97.9 million and $81.7 million, respectively, for our quarterly dividend payments. Our quarterly dividend payments have increased due to regular quarterly increases in our quarterly dividend per share amounts. Principal payments under our finance lease obligations were $9.1 million, $10.3 million and $11.2 million for 2019, 2018 and 2017, respectively, and are impacted by the timing and extent of our network expansion activities. Our financing activities also include proceeds from and repayments of our debt offerings. In June 2019 we received net proceeds of $152.1 million from the issuance of our €135.0 million of 2024 Notes. In August 2018 we received net proceeds of $69.9 million from the issuance of our $70.0 million of senior secured notes. Total installment payment agreement principal payments were $10.0 million, $9.4 million and $3.8 million for 2019, 2018 and 2017, respectively.
Table:
 |  | Year Ended December 31, | 
 | 2019 | 2018 | 2017
 |  | (in thousands) | 
Net cash provided by operating activities | $ 148,809 | $ 133,921 | $ 111,702
Net cash used in investing activities | (46,958) | (49,937) | (45,801)
Net cash provided by (used in) financing activities | 22,020 | (52,545) | (97,267)
Effect of exchange rates on cash | (542) | (2,357) | 4,058
Net increase (decrease) in cash and cash equivalents |  |  | 
during the year | $ 123,329 | $ 29,082 | $ (27,308)


Question: What is the average net cash provided by operating activities in 2017 and 2018?
Answer: 122811.5
Calculation: (111,702 + 133,921)/2