NOTES TO CONSOLIDATED FINANCIAL STATEMENTS stock and warrants, based on the treasury stock method, convertible debentures and preferred stock, based on the if-converted method, and other commitments to be settled in common stock. The calculations of basic and diluted net income (loss) attributable to common shareholders per share and basic and diluted weighted average shares outstanding are as follows (in thousands, except per share data): The following dilutive effect of potential common shares was excluded from the calculation of dilutive weighted average shares outstanding as their effect would be anti-dilutive (in thousands): Financial instruments that potentially subject the Company to concentrations of credit risk are principally cash and cash equivalents, short-term investments, accounts receivable and installments receivable. The Company places its cash and cash equivalents and investments in highly rated institutions. Concentration of credit risk with respect to receivables is limited to certain customers (end users and distributors) to which the Company makes substantial sales. To reduce risk, the Company routinely assesses the financial strength of its customers, hedges specific foreign installments receivable and routinely sells its installments receivable to financial institutions with limited recourse and without recourse. As a result, the Company believes that the accounts and installments receivable credit risk exposure is limited. As of June 30, 2002 and 2003, the Company had no customers that represented 10% of total accounts and installments receivable. The Company makes judgments as to its ability to collect outstanding receivables and provide allowances for the portion of receivables when it is probable that a loss has been incurred. Provisions are made based upon a specific review of all significant outstanding invoices. In determining these provisions, the Company analyzes its historical collection experience and current economic trends. Financial instruments consist of cash and cash equivalents, short-term investments, accounts receivable, installments receivable, foreign exchange contracts and 5$^{1}$/ 4 % convertible subordinated debentures. The estimated fair value of these financial instruments approximates their carrying value and, except for accounts receivable and installments receivable, is based primarily on market quotes. Years Ended June 30 2001 2002 2003 Net income (loss) attributable to common shareholders $(20,375) $(83,466) $(170,017) Basic weighted average common shares outstanding 29,941 32,308 38,476 Weighted average potential common shares — — — Diluted weighted average shares outstanding 29,941 32,308 38,476 Basic net income (loss) attributable to common shareholders per share $ (0.68) $ (2.58) $ (4.42) Diluted net income (loss) attributable to common shareholders per share $ (0.68) $ (2.58) $ (4.42) Years Ended June 30 2001 2002 2003 Convertible debt 1,628 1,628 1,628 Convertible preferred stock — 1,113 3,135 Obligation subject to common stock settlement — 1,043 — Preferred stock dividend, to be settled in common stock — 23 184 Options, restricted stock and warrants 2,897 1,173 920 Total 4,525 4,980 5,867 (k) Concentration of Credit Risk (l) Allowance for Doubtful Accounts (m) Financial Instruments 40