Receivables, net are reported net of an allowance for credit losses. Management evaluates the aging of customer receivable balances, the financial condition of our customers, historical trends, and macroeconomic factors to estimate the amount of customer receivables that may not be collected in the future and records a provision it believes is appropriate. Our reserve for expected lifetime credit losses was $68 million and $70 million as of March 31, 2021 and December 31, 2020, respectively. Bad debt expense totaled $2 million and $9 million for the three months ended March 31, 2021 and 2020, respectively.

Aftermarket and refurbished products and salvage and remanufactured products are primarily composed of finished goods. As of March 31, 2021, manufactured products inventory was composed of $17 million of raw materials, $4 million of work in process, and $2 million of finished goods. As of December 31, 2020, manufactured products inventory was composed of $16 million of raw materials, $3 million of work in process, and $2 million of finished goods.

Goodwill and indefinite-lived intangible assets are tested for impairment at least annually. We performed our annual impairment test during the fourth quarter of 2020 and we determined no impairment existed as all of our reporting units had a fair value estimate which exceeded the carrying value by at least 30%. Goodwill impairment testing may also be performed on an interim basis when events or circumstances arise that may lead to impairment. The fair value estimates of our reporting units were established using weightings of the results of a discounted cash flow methodology and a comparative market multiples approach. We did not identify a triggering event in the first quarter of 2021 that necessitated an interim test of goodwill impairment or indefinite-lived intangible assets impairment.

Our investment in unconsolidated subsidiaries in Europe was $150 million and $137 million as of March 31, 2021 and December 31, 2020, respectively. We recorded equity in earnings of $6 million and $1 million during the three months ended March 31, 2021 and 2020, respectively, mainly related to our investment in Mekonomen AB ("Mekonomen").

On December 1, 2016, we acquired a 26.5% equity interest in Mekonomen for an aggregate purchase price of $181 million. In October 2018, we acquired an additional $48 million of equity in Mekonomen at a discounted share price as part of its rights issue, increasing our equity interest to 26.6%. We are accounting for our interest in Mekonomen using the equity method of accounting, as our investment gives us the ability to exercise significant influence, but not control, over the investee. As of March 31, 2021, our share of the book value of Mekonomen's net assets exceeded the book value of our investment in Mekonomen by $7 million; this difference is primarily related to Mekonomen's Accumulated Other Comprehensive Income balance as of our acquisition date in 2016. We are recording our equity in the net earnings of Mekonomen on a one quarter lag.

Mekonomen announced in March 2020 and February 2021, respectively, that the Mekonomen Board of Directors proposed no dividend payment in 2020 or 2021. The Level 1 fair value of our equity investment in the publicly traded Mekonomen common stock at March 31, 2021 was $230 million (using the Mekonomen share price of SEK 129 as of March 31, 2021) compared to a carrying value of $139 million.

Some of our salvage mechanical products are sold with a standard six month warranty against defects. Additionally, some of our remanufactured engines are sold with a standard three or four year warranty against defects. We also provide a limited lifetime warranty for certain of our aftermarket products. These assurance-type warranties are not considered a separate performance obligation, and thus no transaction price is allocated to them. We record the warranty costs in Cost of goods sold in our Unaudited Condensed Consolidated Statements of Income. Our warranty reserve is calculated using historical claim information to project future warranty claims activity and is recorded within Other accrued expenses and Other noncurrent liabilities on our Unaudited Condensed Consolidated Balance Sheets based on the expected timing of the related payments.

We have certain contingencies resulting from litigation, claims and other commitments and are subject to a variety of environmental and pollution control laws and regulations incident to the ordinary course of business. We currently expect that the resolution of such contingencies will not materially affect our financial position, results of operations or cash flows.

During the three months ended March 31, 2021, we recorded $9 million in financial assistance from foreign governments, primarily in the form of grants, of which $7 million and $2 million related to Europe and Canada, respectively. For the three months ended March 31, 2021, an immaterial amount was recorded as a reduction to Cost of goods sold, and $9 million was a reduction to Selling, general and administrative expenses, in our Unaudited Condensed Consolidated Statement of Income. Financial assistance received from governments is recorded during the period in which we incur the costs that the assistance is intended to offset (and only if it is probable that we will meet the conditions required under the terms of the assistance). No government assistance was recorded for the three months ended March 31, 2020.

The amount disclosed for Leased assets obtained in exchange for operating lease liabilities for the three months ended March 31, 2020 in the supplemental disclosure of noncash investing and financing activities in the Unaudited Condensed Consolidated Statements of Cash Flows includes an immaterial correction of $18 million to address an omission of the impact of lease modifications and terminations.

As of March 31, 2021, our Board of Directors had authorized a stock repurchase program under which we may purchase up to $1.0 billion of our common stock from time to time through October 25, 2022. Repurchases under the program may be made in the open market or in privately negotiated transactions, with the amount and timing of repurchases depending on market conditions and corporate needs. The repurchase program does not obligate us to acquire any specific number of shares and may be suspended or discontinued at any time.

During the three months ended March 31, 2021, we repurchased 1.5 million shares of common stock for an aggregate price of $57 million. During the three months ended March 31, 2020, we repurchased 3.3 million shares of common stock for an aggregate price of $88 million. As of March 31, 2021, there was $474 million of remaining capacity under our repurchase program. Repurchased shares are accounted for as treasury stock using the cost method.

In February 2020, as part of the sale of Stahlgruber's Czech Republic business, we divested the noncontrolling interest of the business, which resulted in a net decrease to Noncontrolling interest of $11 million in our unaudited condensed consolidated financial statements as of March 31, 2020. See Note 2, "Discontinued Operations," for further information.

In December 2019, we modified the shares of a noncontrolling interest of a subsidiary acquired in connection with the Stahlgruber acquisition and issued new redeemable shares to the minority shareholder. The new redeemable shares contain (i) a put option for all noncontrolling interest shares at a fixed price of $24 million (€21 million) for the minority shareholder exercisable in the fourth quarter of 2023, (ii) a call option for all noncontrolling interest shares at a fixed price of $26 million (€23 million) for the Company exercisable beginning in the first quarter of 2026 through the end of the fourth quarter of 2027, and (iii) a guaranteed dividend to be paid quarterly to the minority shareholder through the fourth quarter of 2023. The new redeemable shares do not provide the minority shareholder with rights to participate in the profits and losses of the subsidiary prior to the exercise date of the put option. As the put option is outside the control of the Company, we recorded a $24 million Redeemable noncontrolling interest at the put option's redemption value outside of permanent equity on our Unaudited Condensed Consolidated Balance Sheets.

In the first quarter of 2021, we adopted ASU No. 2019-12, "Income Taxes" (Topic 740) ("ASU 2019-12"), which simplifies the accounting for income taxes and adds guidance to reduce complexity in certain areas. We adopted the standard in the first quarter using the prospective approach. The adoption of this accounting standard did not have a material impact on our unaudited condensed consolidated financial statements.

In March 2020, the FASB issued ASU No. 2020-04, "Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting" ("ASU 2020-04"), which provides temporary optional guidance to ease the potential burden in accounting for reference rate reform. ASU 2020-04 provides optional expedients and exceptions for applying generally accepted accounting principles to transactions affected by reference rate reform if certain criteria are met. These transactions include contract modifications, hedging relationships, and sale or transfer of debt securities classified as held-to-maturity. Entities may apply the provisions of the new standard as of the beginning of the reporting period when the election is made (i.e., as early as the first quarter of 2020). Unlike other topics, the provisions of this update are only available until December 31, 2022. We are currently evaluating the impact of this standard on our consolidated financial statements and related disclosures, and we have not yet elected an adoption date.