The Company generates a significant portion of its sales in the United States; however, several of its products are sold into various foreign countries, which subject the Company to the risks of doing business abroad. In addition, the Company operates in the footwear industry, which is impacted by the general economy, and its business depends on the general economic environment and levels of consumer spending. Changes in the marketplace may significantly affect the Company’s estimates and its performance. The Company performs regular evaluations concerning the ability of customers to satisfy their obligations and provides for estimated doubtful accounts. Domestic accounts receivable, which generally do not require collateral from customers, amounted to $228.5 million and $213.7 million before allowances for bad debts and sales returns, and chargebacks at December 31, 2019 and 2018, respectively. Foreign accounts receivable, which are generally collateralized by letters of credit, amounted to $440.9 million and $313.8 million before allowance for bad debts, sales returns, and chargebacks at December 31, 2019 and 2018, respectively. International sales amounted to $3,022.6 million, $2,514.0 million and $2,108.7 million for the years ended December 31, 2019, 2018 and 2017, respectively. The Company’s credit losses charged to expense for the years ended December 31, 2019, 2018 and 2017 were $31.6 million, $8.0 million and $12.8 million, respectively. In addition, the Company recorded sales return expense for the years ended December 31, 2019, 2018 and 2017 were $46.1 million, $20.2 million and $5.6 million, respectively.

Assets located outside the United States consist primarily of cash, accounts receivable, inventory, property, plant and equipment, and other assets. Net assets held outside the United States were $2,643.8 million and $1,611.2 million at December 31, 2019 and 2018, respectively.

During 2019, 2018 and 2017, no customer accounted for 10.0% or more of sales. No customer accounted for more than 10% of net trade receivables at December 31, 2019 or 2018. During 2019, 2018 and 2017, sales to the five largest customers were approximately 9.6%, 10.4% and 10.5%, respectively.

The Company’s top five manufacturers produced the following for the years ended December 31, 2019, 2018 and 2017, respectively:

The majority of the Company’s products are produced in China and Vietnam. The Company’s operations are subject to the customary risks of doing business abroad, including but not limited to currency fluctuations and revaluations, custom duties and related fees, various import controls and other monetary barriers, restrictions on the transfer of funds, labor unrest and strikes and, in certain parts of the world, political instability. The Company believes it has acted to reduce these risks by diversifying manufacturing among various factories. To date, these business risks have not had a material adverse impact on the Company’s operations.