Total interest expense increased $2.3 million, or 10.7%, during the six months ended June 30, 2021, compared to the 2020 period, primarily as a result of decreased capitalized interest due to placing LA3 Phase 1 into service during the twelve months ended June 30, 2021. In addition, the weighted average principal debt outstanding was $1.8 billion and $1.6 billion during the six months ended June 30, 2021, and 2020, respectively. This increase was partially offset by a decrease in our daily weighted average interest rate to 3.06% during the six months ended June 30, 2021 from 3.27% during the six months ended June 30, 2020.
Liquidity and Capital Resources
Discussion of Cash Flows
Six Months Ended June 30, 2021, Compared to the Six Months Ended June 30, 2020
Operating Activities
Net cash provided by operating activities was $145.3 million for the six months ended June 30, 2021, compared to $137.5 million for the six months ended June 30, 2020. The increase of $7.8 million, or 5.6%, was driven by organic growth of our operating cash flows as a result of leasing activity within spaces recently placed into service, including SV8 Phase 3 and LA3 Phase 1, and at our LA2 and VA3 data centers. The increase was partially offset by the timing of vendor payments and customer receipts.
Investing Activities
Net cash used in investing activities decreased by $93.3 million, or 60.3%, to $61.3 million for the six months ended June 30, 2021, compared to $154.7 million for the six months ended June 30, 2020. This decrease was primarily due to lower construction expenditures after placing SV8 Phase 3, CH2 Phase 1, and LA3 Phase 1 into service during the year ended December 31, 2020.
Financing Activities
Net cash used in financing activities was $86.6 million during the six months ended June 30, 2021, compared to $16.8 million provided by financing activities during the six months ended June 30, 2020.
During the six months ended June 30, 2021, we received cash proceeds, net of payments, of $34.0 million from borrowings under the revolving credit facility. During the six months ended June 30, 2020, we received cash proceeds, net of payments, of $36.5 million from borrowings under the revolving credit facility.
During the six months ended June 30, 2020, we received $100 million of cash proceeds from the issuance of the 2027 senior unsecured notes.
We paid $120.6 million in dividends and distributions on our common stock and Operating Partnership units during the six months ended June 30, 2021, compared to $118.8 million during the six months ended June 30, 2020, as a result of an increase in our quarterly dividend to $2.46 per share or unit paid during the six months ended June 30, 2021, from $2.44 per share or unit paid during the six months ended June 30, 2020.
Analysis of Liquidity and Capital Resources
We have an effective shelf registration statement that allows us to offer for sale various unspecified classes of equity and debt securities. As circumstances warrant, we may issue debt and/or equity securities from time to time on an opportunistic basis, dependent upon market conditions and available pricing. We make no assurance that we can issue and sell such securities on acceptable terms or at all.
Our short-term liquidity requirements primarily consist of funds needed for interest expense, operating costs, including utilities, site maintenance costs, real estate and personal property taxes, insurance, rental expenses, sales and marketing and general and administrative expenses, certain capital expenditures, including for the development of data center