NOI for our Same-Store Community properties decreased 4.1%, or $20.8 million, for the nine months ended September 30, 2020 compared to the same period in 2019. The decrease in property NOI was attributable to a 1.9%, or $13.3 million, decrease in property rental income and a 3.7%, or $7.5 million, increase in operating expenses. The decrease in property rental income was primarily driven by a $7.5 million increase in our reserve on multifamily tenant lease receivables, an increase of $8.2 million in rent concessions and an increase of $8.0 million in occupancy loss, partially offset by a 1.6%, or $10.4 million, increase in rental rates and a 0.4%, or $0.3 million, increase in reimbursement and ancillary and fee income. Physical occupancy decreased by 0.5% to 96.3% and total monthly income per occupied home decreased 1.3% to $2,148.
The increase in operating expenses was primarily driven by a 6.7%, or $5.6 million, increase in real estate taxes, which was primarily due to higher assessed valuations, and a 12.4%, or $3.5 million, increase in repair and maintenance expense due to the increased use of third party vendors, partially offset by a 7.1%, or $2.9 million, decrease in personnel expense as a result of fewer employees.
The operating margin (property net operating income divided by property rental income) was 70.1% and 71.7% for the nine months ended September 30, 2020 and 2019, respectively.
Non-Mature Communities/Other
UDR’s Non-Mature Communities/Other represent those communities that do not meet the criteria to be included in Same-Store Communities, which include communities recently developed or acquired, redevelopment properties, sold or held for disposition properties, and non-apartment components of mixed use properties.
Three Months Ended September 30, 2020 vs. Three Months Ended September 30, 2019
The remaining 20.5%, or $43.3 million, of our total NOI during the three months ended September 30, 2020 was generated from our Non-Mature Communities/Other. NOI from Non-Mature Communities/Other increased by 161.6%, or $26.8 million, for the three months ended September 30, 2020 as compared to the same period in 2019. The increase was primarily attributable to an $18.2 million increase in stabilized, non-mature communities NOI due to operating communities acquired in 2020 and 2019 and an $11.1 million increase in non-residential/other primarily due to changes in straight-line rent as a result of increased tenant rent concessions during the period, partially offset by a $1.9 million decrease in NOI from sold and held for disposition communities.
Nine Months Ended September 30, 2020 vs. Nine Months Ended September 30, 2019
The remaining 24.4%, or $158.3 million, of our total NOI during the nine months ended September 30, 2020 was generated from our Non-Mature Communities/Other. NOI from Non-Mature Communities/Other increased by 93.8%, or $76.6 million, for the nine months ended September 30, 2020 as compared to the same period in 2019. The increase was primarily attributable to a $65.9 million increase in stabilized, non-mature communities NOI due to operating communities acquired in 2020 and 2019, a $10.1 million increase in non-residential/other primarily due to changes in straight-line rent as a result of increased tenant rent concessions during the period and a $4.2 million increase in acquired communities, partially offset by a $2.4 million decrease in NOI from redevelopment communities.
Real estate depreciation and amortization
For the three months ended September 30, 2020 and 2019, the Company recognized real estate depreciation and amortization of $151.9 million and $127.4 million, respectively. The increase in 2020 as compared to 2019 was primarily attributable to communities acquired in 2020 and 2019, partially offset by a decrease from fully depreciated assets.
For the nine months ended September 30, 2020 and 2019, the Company recognized real estate depreciation and amortization of $462.5 million and $357.8 million, respectively. The increase in 2020 as compared to 2019 was primarily attributable to communities acquired in 2020 and 2019, partially offset by a decrease from fully depreciated assets.
Gain/(Loss) on sale of real estate owned
During the nine months ended September 30, 2020, the Company recognized gains of $61.3 million from the sale of two operating communities located in Kirkland, Washington and Bellevue, Washington. During the nine months ended September 30, 2019, the Company recognized a gain of $5.3 million on the sale of a parcel of land in Los Angeles, California.