Notes to the Consolidated Financial Statements 72 2019 PPG ANNUAL REPORT AND 10-K Remediation: Reasonably Possible Matters In addition to the amounts currently reserved for environmental remediation, the Company may be subject to loss contingencies related to environmental matters estimated to be as much as $100 million to $200 million. Such unreserved losses are reasonably possible but are not currently considered to be probable of occurrence. These reasonably possible unreserved losses relate to environmental matters at a number of sites, none of which are individually significant. The loss contingencies related to these sites include significant unresolved issues such as the nature and extent of contamination at these sites and the methods that may have to be employed to remediate them. The impact of evolving programs, such as natural resource damage claims, industrial site re-use initiatives and domestic and international remediation programs, also adds to the present uncertainties with regard to the ultimate resolution of this unreserved exposure to future loss. The Company’s assessment of the potential impact of these environmental contingencies is subject to considerable uncertainty due to the complex, ongoing and evolving process of investigation and remediation, if necessary, of such environmental contingencies, and the potential for technological and regulatory developments. 15. Shareholders' Equity A class of 10 million shares of preferred stock, without par value, is authorized but unissued. Common stock has a par value of $1.66 2 / 3 per share; 1.2 billion shares are authorized. Common Stock Treasury Stock Shares Outstanding January 1, 2017 581,146,136 (323,815,976) 257,330,160 Purchases — (7,427,557) (7,427,557) Issuances — 1,271,796 1,271,796 December 31, 2017 581,146,136 (329,971,737) 251,174,399 Purchases — (15,877,364) (15,877,364) Issuances — 564,399 564,399 December 31, 2018 581,146,136 (345,284,702) 235,861,434 Purchases — (2,722,800) (2,722,800) Issuances — 2,541,836 2,541,836 December 31, 2019 581,146,136 (345,465,666) 235,680,470 Per share cash dividends paid were $1.98, $1.86 and $1.70 in 2019, 2018 and 2017, respectively.