Thirty-Nine Weeks Ended October 31, 2020 Compared to Thirty-Nine Weeks Ended November 2, 2019
Net Sales. Net sales increased by $385.3 million, or 61.3%, to $ 1,013.6 million during the 39 weeks ended October 31, 2020 compared to $628.3 million in the corresponding period of fiscal year 2019. Our net sales increased due to a variety of reasons including: increased demand driven by the exit of competitors and market share gains due to increase participation in outdoor activities, increased demand through our e-commerce platform, demand driven by the change in consumer behavior associated with the COVID-19 pandemic, and increased demand due to the presidential election. Stores that were opened in fiscal year 2020 and stores that have been open for less than 12 months and were, therefore, not included in our same store sales, contributed $120.4 million to net sales. Same store sales also increased by 44.4% for the 39 weeks ended October 31, 2020 compared to the comparable 39 week period of fiscal year 2019, primarily driven by increases in our hunting and shooting department due to the drivers of increased demand discussed above.
All of our departments had increases in net sales for the 39 weeks ended October 31, 2020 compared to the corresponding period in fiscal year 2019, led by our hunting and shooting department with an increase in net sales of $270.9 million, or 91.0%. Our camping, fishing, apparel, footwear, and optics, electronics, and accessories departments also had increases in net sales of $42.5 million, $36.2 million, $11.1 million, $7.5 million and $16.9 million, respectively, in the 39 weeks ended October 31, 2020 compared to the comparable 39-week period of fiscal year 2019 due to increased traffic within our stores and online. Within hunting, our firearm and ammunition categories saw increases of $135.5 million, or 121.7%, and $84.3 million, or 92.6%, respectively, in the 39 weeks ended October 31, 2020 compared to the comparable 39-week period of fiscal year 2019, which increases resulted from the drivers of increased demand discussed above.
Each of our departments had increases in same store sales for the 39 weeks ended October 31, 2020 compared to the corresponding period in fiscal year 2019, led by our hunting and shooting department with an increase in same store sales of 66.8%. Our camping, fishing, optics, electronics and accessories, footwear, and apparel departments had increases in same store sales of 32.0%, 29.7%, 24.6%, 6.8%, and 5.5% respectively, for the 39-weeks ended October 31, 2020 compared to the comparable 39-week period of fiscal year 2019. As of October 31, 2020, we had 94 stores included in our same store sales calculation.
Gross Profit. Gross profit increased to $334.5 million during the 39 weeks ended October 31, 2020 compared to $211.6 million for the corresponding period of fiscal year 2019. As a percentage of net sales, gross profit decreased to 33.0% for the 39 weeks ended October 31, 2020, compared to 33.7% for the corresponding period of fiscal year 2019 due to the change in product mix in the quarter as a result of the majority of revenue being generated from lower margin categories such as firearms and ammunition and a channel mix shift to higher e-commerce driven sales causing increased freight costs. The gross margin decline was partially offset by higher product margins, volume incentives, and other adjustments, which positively impacted gross margin.
Selling, General, and Administrative Expenses. Selling, general, and administrative expenses increased by $59.8 million, or 31.2%, to $251.1 million during the 39 weeks ended October 31, 2020 from $191.3 million for the comparable 39-week period of fiscal year 2019. This increase was primarily due to an increase in our payroll expense of $34.4 million, which mostly resulted from the opening of 10 new stores since the end of the third quarter of fiscal year 2019, minimum wage increases impacting 62 of our stores in fiscal year 2020 and the payment of $4.6 million in hazard pay. We also had increases in other selling, general, and administration expenses, rent, and depreciation of $16.6 million due to increased credit card fees, $6.8 million, and $2.7 million, which includes $0.8 million of asset write-offs relating to the closing of one store during the first quarter, respectively, primarily related to the opening of 10 new stores since November 2, 2019. As a percentage of net sales, selling, general, and administrative expenses decreased to 24.8% of net sales in the three quarters of fiscal year 2020, compared to 30.5% of net sales in the three quarters of fiscal year 2019, primarily as a result of the significant increase in net sales we experienced in the 39 weeks ended October 31, 2020 compared to the corresponding period in fiscal year 2019.
Interest Expense. Interest expense decreased by $3.6 million, or 52.9%, to $3.0 million during the 39 weeks ended October 31, 2020 from $6.6 million for the comparable 39-week period of fiscal year 2019. Interest expense decreased primarily as a result of our lower debt balances during the 39 weeks ended October 31, 2020 compared to the corresponding period of fiscal year 2020 as noted above.
Income Taxes. We recognized an income tax expense of $20.7 million and $3.2 million during the 39 weeks ended October 31, 2020 and November 2, 2019, respectively. Our effective tax rate for the 39 weeks ended October 31, 2020