decreased by $0.6 million primarily due to the sale of two of the five buildings in the complex in May 2017 and Washington Group Plaza decreased by $4.9 million due to the sale of the property in March 2018. The remaining properties’ revenues were modestly higher in comparison to nine months ended September 30, 2017 as a result of modestmark-to-market increases in rents.
Rental Income. Rental income includes net rental income and income from a ground lease. Total rental income increased $15.7 million, or 24%, to $81.1 million for the nine months ended September 30, 2018 compared to $65.4 million for the nine months ended September 30, 2017. The increase in rentalincome wasprimarily due to the acquisitions described above. The acquisitions of Mission City, Sorrento Mesa, Papago Tech, Pima Center, Circle Point and The Quad contributed an additional $5.9 million, $6.8 million, $2.6 million, $3.4 million, $1.0 million and $0.8 million in rental income, respectively,to the 2018 period rental income. Central Fairwinds and Park Tower also increased by $0.1 and $0.2 million, respectively, as a result of increased occupancy over the prior year. AmberGlen decreased by $0.5 million primarily due to the sale of two of the five buildings in the complex in May 2017 and Washington Group Plaza decreased by $4.9 million due to the sale of that property in March 2018. The remaining properties’ rental income were modestly higher in comparison to nine months ended September 30, 2017 as a result of modestmark-to-market increases in rents.
Expense Reimbursement. Total expense reimbursement increased $3.9 million, or 51%, to $11.6 million for the nine month period ended September 30, 2018 compared to $7.7 million for the same period in 2017, primarily due to the acquisition of the 2525 McKinnon, Mission City, Sorrento Mesa, Papago Tech, Pima Center, Circle Point and The Quad properties described above.
Other. Other revenue includes parking, signage and other miscellaneous income. Total other revenues increased $0.4 million, or 19%, to $2.6 million for the nine month period ended September 30, 2018 compared to $2.2 million for the same period in 2017. The increase can be attributed to the net proceeds of an auction of a former tenant’s equipment at FRP Collection which vacated unexpectedly late in 2017. Nominal other income was also generated by City Center, Central Fairwinds, Logan Tower, DTC Crossroads, 5090 N 40th St, SanTan, 2525 McKinnon, Park Tower, Mission City and Sorrento Mesa with the largest contribution from City Center and Park Tower parking income.
Operating Expenses
Total Operating Expenses. Total operating expenses consist of property operating expenses, general and administrative expenses and depreciation and amortization. Total operating expenses increased by $14.2 million, or 22%, to $79.5 million for the nine months ended September 30, 2018, from $65.3 million for the same period in 2017, primarily due to acquisitions described above. Total operating expenses increased by $6.4 million, $5.9 million, $2.0 million, $3.6 million, $1.7 million and $1.0 million, respectively, from the acquisitions of Mission City, Sorrento Mesa, Papago Tech, Pima Center, Circle Point and The Quad properties. AmberGlen decreased by $0.4 million primarily due to the sale of two of the five buildings in the complex in May 2017. Washington Group Plaza operating expenses decreased by $3.5 million due to its sale in March 2018. The remaining operating expenses aggregated to an overall $2.5 million decrease in comparison to the prior year primarily related to a decrease in depreciation at FRP Collection.
Property Operating Expenses. Property operating expenses are comprised mainly of building common area and maintenance expenses, insurance, property taxes, property management fees, as well as certain expenses that are not recoverable from tenants, the majority of which are related to costs necessary to maintain the appearance and marketability of vacant space. In the normal course of business, property expenses fluctuate and are impacted by various factors including, but not limited to, occupancy levels, weather, utility costs, repairs, maintenance andre-leasing costs. Property operating expenses increased $5.6 million, or 18%, to $36.6 million for the nine months ended September 30, 2018 from $31.0 million for the same period in 2017. The increase in property operating expenses was primarily due to the acquisitions described above. The acquisition of the Mission City, Sorrento Mesa, Papago Tech, Pima Center, Circle Point and The Quad contributed an additional $3.0 million, $1.7 million, $0.8 million, $1.4 million, $0.7 million and $0.2 million in additional property operating expenses, respectively. AmberGlen decreased by $0.3 million primarily due to the sale of two of the five buildings in the complex in May 2017, and Washington Group Plaza decreased by $2.3 million due to the sale of that property in March 2018. The remaining property operating expenses aggregate to an overall $0.4 million increase in comparison to the prior year.
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