Member2017-11-172017-11-1700015976722017-11-170001597672ryam:TembecInc. Therefore, our customers demand products of the highest quality. Product qualification time can be lengthy, extending six to twenty-four months. Some competitors use both wood and cotton linter fibers, as a source of cellulose fibers. We compete with both domestic and foreign producers of commodity products. For commodity viscose, major competitors include Sappi, Austrocell and Bracell. ProductsWe manufacture finished dimensional lumber (2 by 4's, 2 by 8's, etc.) Additionally, bark and sawdust are used for fuel in several of our operations. PaperboardWe manufacture paperboard in the Temiscaming plant in Quebec. To a lesser extent, quality and service are also considered competitive determinants. Pulp & NewsprintWe manufacture and market high-yield pulp and newsprint. We do not foresee any material constraints in the near term from pricing or availability. Our U.S. patents generally have a duration of 20 years from the date of filing. We also require key employees to enter into non-compete agreements as appropriate. SeasonalityOur operating results are not significantly affected by seasonal changes. We have strong and open relationships with these employee representatives. DiversityRespect for people is one of Rayonier Advanced Materials core values. Our diversity allows us to learn and build solutions from different perspectives. We track the progress against these metrics monthly with an annual goal of improvement. Likewise, volumes have declined meaningfully in recent years due to these factors. The COVID-19 pandemic has exacerbated these dynamics and may continue to do so. We have manufacturing operations in the United States, Canada and France. We are also subject to credit risk associated with these customers. It is unclear whether these conditions will persist into the future. As of December 31, 2020, approximately 75 percent of our global work force is unionized. The potential longer-term impacts of climate-related risks remain uncertain at this time. On the other hand, Ontario is subjected to the federal program. In addition, our actual cash requirements in the future may be greater than expected. We may need to seek additional financing for general corporate purposes. As a result, production capacities may vary from the amounts listed above. Since 2017, we have paid a total of $91 million in duties. The majority of our contracts have a single performance obligation to transfer products. Accordingly, we recognize revenue when control has been transferred to the customer. Gains and losses on the retirement of assets are included in operating income. This evidence supports the realizability of most recorded deferred tax assets. Tax assets are reviewed periodically for realizability. See discussion in the Forest Products portion of the Results of Operations herein. For additional information, see Note 10 — Debt and Finance Leases. See Note 18 — Employee Benefit Plans. The 2019 effective tax rate from continuing operations was a benefit of 20 percent. Total net sales decreased $76 million, or 7 percent, in 2020. Operating income remained essentially flat in 2020 when compared to the prior year. Paperboard sales prices declined 2 percent due to increased competition. Pulp sales volumes increased 5 percent. The decrease was primarily driven by lower sales prices and higher costs. Total net sales declined $67 million, or 24 percent, in 2019. In addi
