pre_text: Results of Operations The following table sets forth the percentage of revenue for certain items in our statements of operations for the periods indicated: Impact of inflation and product price changes on our revenue and on income was immaterial in 2019, 2018 and 2017.
table: Fiscal Years
table: 2019 2018 2017
table: Statements of Operations:
table: Revenue 100% 100% 100%
table: Cost of revenue 43% 50% 55%
table: Gross profit 57% 50% 45%
table: Operating expenses:
table: Research and development 120% 79% 79%
table: Selling, general and administrative 86% 79% 81%
table: Loss from operations (149)% (108)% (115)%
table: Interest expense (3)% (1)% (1)%
table: Interest income and other expense, net 2% 1% —%
table: Loss before income taxes (150)% (108)% (116)%
table: Provision for income taxes 1% 1% 1%
table: Net loss (151)% (109)% (117)%
question: Analyse this data from a financial earnings document. What is the total proportion of cost of revenue as a percentage of revenue in 2017 and 2018?