Our gross profit tends to vary with the mix of revenues we derive from the sale of new vehicles, used vehicles, finance and insurance products, and service and parts transactions. Our gross profit varies across product lines, with vehicle sales usually resulting in lower gross profit margins and our other revenues resulting in higher gross profit margins. Factors such as inventory and vehicle availability, customer demand, consumer confidence, unemployment, general economic conditions, seasonality, weather, credit availability, fuel prices, and manufacturers’ advertising and incentives also impact the mix of our revenues, and therefore influence our gross profit margin.
Aggregate revenue and gross profit increased $372.4 million and $78.4 million, or 7.2% and 10.5%, respectively, during the three months ended September 30, 2017 and increased $758.2 million and $174.9 million, or 5.0% and 7.8%, respectively, during the nine months ended September 30, 2017, compared to the same periods in 2016. The increases are largely attributable to increases in used vehicle, finance and insurance, and service and parts revenue and gross profit from net dealership acquisitions.
Additionally, as our various exchange rates fluctuate, our revenue and results of operations as reported in U.S. Dollars fluctuate. For example, if the British Pound were to weaken against the U.S. Dollar, our U.K. results of operations would translate into less U.S. Dollar reported results. The British Pound weakened against the U.S. Dollar during the three and nine months ended September 30, 2017, compared to the same periods in 2016, which negatively impacted our reported results of operations. On June 23, 2016, the United Kingdom held a referendum in which a majority voted to exit the European Union (“Brexit vote”). The British Pound has weakened since the Brexit vote, with an average exchange rate of British Pounds to U.S. Dollars of 1.309 and 1.276 for the three and nine months ended September 30, 2017, respectively, compared to 1.313 and 1.393 for the same periods in 2016, a decrease of 0.3% and 8.4%, respectively. Foreign currency average rate fluctuations increased revenue and gross profit by $19.0 million and $3.1 million, respectively, for the three months ended September 30, 2017, and decreased revenue and gross profit by $453.4 million and $58.4 million, respectively, for the nine months ended September 30, 2017. Foreign currency average rate fluctuations reduced earnings per share from continuing operations by approximately $0.12 per share for the nine months ended September 30, 2017, and had no per share impact for the three months ended September 30, 2017. Excluding the impact of foreign currency average rate fluctuations, revenue and gross profit increased 6.9% and 10.1%, respectively, for the three months ended September 30, 2017, and increased 8.0% and 10.4%, respectively, for the nine months ended September 30, 2017.
Our selling expenses consist of advertising and compensation for sales personnel, including commissions and related bonuses. General and administrative expenses include compensation for administration, finance, legal and general management personnel, rent, insurance, utilities and other expenses. As the majority of our selling expenses are variable, and we believe a significant portion of our general and administrative expenses are subject to our control, we believe our expenses can be adjusted over time to reflect economic trends.
Floor plan interest expense relates to financing incurred in connection with the acquisition of new and used vehicle inventories that is secured by those vehicles. Other interest expense consists of interest charges on all of our interest-bearing debt, other than interest relating to floor plan financing, and includes interest relating to our retail commercial truck dealership and commercial vehicle distribution operations. The cost of our variable rate indebtedness is based on the prime rate, defined London Interbank Offered Rate (“LIBOR”), the Bank of England Base Rate, the Finance House Base Rate, the Euro Interbank Offered Rate, the Canadian Prime Rate, or the Australian or New Zealand Bank Bill Swap Rate (“BBSW”).
Equity in earnings of affiliates represents our share of the earnings from our investments in joint ventures and other non-consolidated investments, including PTL.
The results of our commercial vehicle distribution business in Australia and New Zealand are principally driven by the number and types of products and vehicles ordered by our customers.
The future success of our business is dependent upon, among other things, general economic and industry conditions; our ability to consummate and integrate acquisitions; the level of vehicle sales in the markets where we operate; our ability to increase sales of higher margin products, especially service and parts services; our ability to realize returns on our significant capital investment in new and upgraded dealership facilities; the success of our distribution of