Revenue
Revenue from IAA increased $107.6 million, or 9%, to $1,326.8 million for the fiscal year ended December 30, 2018, compared with $1,219.2 million for the fiscal year ended December 31, 2017. The increase in revenue was a result of an increase in vehicles sold of approximately 5% for the fiscal year ended December 30, 2018. Revenue per vehicle sold increased 4% for the fiscal year ended December 30, 2018 compared with the fiscal year ended December 31, 2017, partially offset by a decrease of $5.2 million from HBC, which included an increase in revenue of $1.3 million due to fluctuations in the U.K. exchange rate. IAA's North American same-store total loss vehicle inventory increased approximately 1% at December 30, 2018, as compared to December 31, 2017. North American online sales volumes for IAA for the fiscal years ended December 30, 2018 and December 31, 2017 each represented over 60% of the total vehicles sold. The balance of North American vehicles were sold to buyers present at a physical IAA auction.
Most of the vehicles that are sold through our auctions are consigned to IAA by insurance companies and held at IAA’s facilities. IAA does not take title to these consigned vehicles and recognizes revenue when a service is performed as requested by the owner of the vehicle. IAA does not record the gross selling price of the consigned vehicles sold at auction as revenue. Conversely, IAA does record the gross selling price of purchased vehicles sold at auction as revenue. Vehicles sold under purchase agreements were approximately 4% and 5% of total salvage vehicles sold for the fiscal years ended December 30, 2018 and 2017, respectively.
Gross Profit
For the fiscal year ended December 30, 2018, gross profit at IAA increased to $505.6 million, or 38.1% of revenue, compared with $441.1 million, or 36.2% of revenue, for the fiscal year ended December 31, 2017. The increase in gross profit was mainly attributable to a 9% increase in revenue, partially offset by a 6% increase in cost of services, which included costs associated with purchase contract vehicles and organic volume growth.
Excluding HBC, IAA's gross profit margin was 38.6% and 36.9% for the fiscal years ended December 30, 2018 and December 31, 2017, respectively. For the fiscal years ended December 30, 2018 and December 31, 2017, HBC had revenue of approximately $32.7 million and $37.9 million, respectively, and cost of services of approximately $26.6 million and $32.2 million, respectively, as fewer of HBC's vehicles were sold under purchase contracts. The entire selling and purchase price of the vehicle is recorded as revenue and cost of services for purchase contracts.
IAA experienced a reduction in gross profit of $6.8 million and $0.3 million for the fiscal years ended December 30, 2018 and December 31, 2017, respectively, related to catastrophic events. Excluding these events (and HBC as noted above), IAA's gross profit margin was 39.5% and 38.3% for the fiscal years ended December 30, 2018 and December 31, 2017, respectively.
Selling, General and Administrative
Selling, general and administrative expenses at IAA increased $10.5 million, or 9%, to $123.8 million for the fiscal year ended December 30, 2018, compared with $113.3 million for the fiscal year ended December 31, 2017. The increase in selling, general and administrative expenses was primarily attributable to increases in compensation expense of $3.5 million, professional fees related to the potential spin-off of $2.8 million, bad debt expense of $1.6 million, incentive-based compensation expense of $1.0 million, supply expenses of $0.8 million, information technology costs of $0.7 and other miscellaneous expenses aggregating $2.4 million, partially offset by decreases in telecom costs of $1.2 million and other professional fees of $1.1 million.
Depreciation and Amortization
Depreciation and amortization increased $4.3 million, or 5%, to $97.4 million for fiscal year ended December 30, 2018, compared with $93.1 million for the fiscal year ended December 31, 2017. The increase in depreciation and amortization was primarily the result of certain assets placed in service over the last twelve months.
Income Taxes
We had an effective tax rate of 25.4% for the fiscal year ended December 30, 2018, compared with an effective tax rate of 18.1% for the fiscal year ended December 31, 2017. Our effective tax rate was higher for the fiscal year ended December 30, 2018, compared with the fiscal year ended December 31, 2017, primarily as a result of the enactment of the Tax Cuts and Jobs Act of 2017 (the “TCJA”) in the fourth quarter of 2017. As a result, in