There have been no changes outside of the ordinary course of business to our contractual obligations as disclosed in our Annual Report on Form 10-K for the year ended December 31, 2020.
Liquidity and Capital Resources
Our cash, cash equivalents, and marketable securities balances decreased by $136.3 million in the six months ended July 4, 2021 to $1,418.1 million.
Operating activities during the six months ended July 4, 2021 provided cash of $244.4 million. Changes in operating assets and liabilities used cash of $373.6 million. This was due to a $470.2 million increase in operating assets and a $96.6 million increase in operating liabilities.
The increase in operating assets was due to a $372.7 million increase in accounts receivable due to greater sales, a $117.4 million increase in prepayments and other assets due to prepayments to our contract manufacturers as a result of higher forecasted revenues, partially offset by a $19.9 million decrease in inventories.
The change in operating liabilities was due to increases of $78.5 million in other accrued liabilities, $22.3 million in accounts payable, and $15.2 million in deferred revenue and customer advance payments, partially offset by a $14.0 million decrease in accrued employee compensation, $2.7 million of retirement plan contributions, and a $2.6 million decrease in income taxes.
Investing activities during the six months ended July 4, 2021 provided cash of $92.3 million due to $460.2 million and $116.1 million in proceeds from maturities and sales of marketable securities, partially offset by $398.1 million used for purchases of marketable securities, $74.0 million used for purchases of property, plant and equipment and $12.0 million used for an investment in MachineMetrics, Inc.(“MachineMetrics”).
Financing activities during the six months ended July 4, 2021 used cash of $295.9 million due to $66.8 million used for payments of convertible debt principal, $196.6 million used for the repurchase of 1.6 million shares of common stock at an average price of $125.69 per share, $31.8 million used for payments related to net settlements of employee stock compensation awards, and $33.3 million used for dividend payments, partially offset by $32.6 million from the issuance of common stock under employee stock purchase and stock option plans.
Operating activities during the six months ended June 28, 2020 provided cash of $266.0 million. Changes in operating assets and liabilities used cash of $206.7 million due to a $384.2 million increase in operating assets and a $177.6 million increase in operating liabilities.
The increase in operating assets was due to a $331.0 million increase in accounts receivable due to increased sales, a $49.5 million increase in prepayments and other assets, and a $3.7 million increase in inventories.
The increase in operating liabilities was due to a $54.9 million increase in accounts payable, a $47.2 million increase in other accrued liabilities, a $37.8 million increase in income taxes, a $28.7 million increase in deferred revenue and customer advance payments, an $11.4 million increase in accrued employee compensation, partially offset by $2.5 million of retirement plan contributions.
Investing activities during the six months ended June 28, 2020 used cash of $173.2 million due to $299.5 million used for purchases of marketable securities, and $84.0 million used for purchases of property, plant and equipment, partially offset by $183.0 million and $26.7 million in proceeds from maturities and sales of marketable securities, respectively, and proceeds from life insurance of $0.5 million related to the cash surrender value from the cancellation of a Teradyne owned life insurance policy, and $0.1 million, net of cash acquired, for the acquisition of AutoGuide.
Financing activities during the six months ended June 28, 2020 used cash of $140.3 million due to $88.5 million used for the repurchase of 1.5 million shares of common stock at an average price of $58.33 per share, $22.5 million used for payments related to net settlements of employee stock compensation awards, $33.3 million used for dividend payments, and $8.9 million used for a payment related to MiR acquisition contingent consideration, partially offset by $12.8 million from the issuance of common stock under employee stock purchase and stock option plans.
In January and May 2021 and 2020, our Board of Directors declared a quarterly cash dividend of $0.10 per share. Dividend payments for each of the six months ended July 4, 2021 and June 28, 2020 were $33.3 million.