2022 secondary market same store communities are generally communities in markets with populations of more than 1 million but less than 1% ( 1 % ) of the total public multifamily reit units or markets with populations of less than 1 million that we have owned and have been stabilized for at least a full 12 months . 2022 non-same store communities and other includes recent acquisitions , communities in development or lease-up , communities that have been identified for disposition , and communities that have undergone a significant casualty loss . also included in non-same store communities are non-multifamily activities . on the first day of each calendar year , we determine the composition of our same store operating segments for that year as well as adjust the previous year , which allows us to evaluate full period-over-period operating comparisons . an apartment community in development or lease-up is added to the same store portfolio on the first day of the calendar year after it has been owned and stabilized for at least a full 12 months . communities are considered stabilized after achieving 90% ( 90 % ) occupancy for 90 days . communities that have been identified for disposition are excluded from the same store portfolio . all properties acquired from post properties in the merger remained in the non-same store and other operating segment during 2017 , as the properties were recent acquisitions and had not been owned and stabilized for at least 12 months as of january 1 , 2017 . for additional information regarding our operating segments , see note 14 to the consolidated financial statements included elsewhere in this annual report on form 10-k . acquisitions one of our growth strategies is to acquire apartment communities that are located in various large or secondary markets primarily throughout the southeast and southwest regions of the united states . acquisitions , along with dispositions , help us achieve and maintain our desired product mix , geographic diversification and asset allocation . portfolio growth allows for maximizing the efficiency of the existing management and overhead structure . we have extensive experience in the acquisition of multifamily communities . we will continue to evaluate opportunities that arise , and we will utilize this strategy to increase our number of apartment communities in strong and growing markets . we acquired the following apartment communities during the year ended december 31 , 2017: .
what the number of units purchased in december 31 , 2017
dispositions we sell apartment communities and other assets that no longer meet our long-term strategy or when market conditions are favorable , and we redeploy the proceeds from those sales to acquire , develop and redevelop additional apartment communities and rebalance our portfolio across or within geographic regions . dispositions also allow us to realize a portion of the value created through our investments and provide additional liquidity . we are then able to redeploy the net proceeds from our dispositions in lieu of raising additional capital . in deciding to sell an apartment community , we consider current market conditions and generally solicit competing bids from unrelated parties for these individual assets , considering the sales price and other key terms of each proposal . we also consider portfolio dispositions when such a structure is useful to maximize proceeds and efficiency of execution . during the year ended december 31 , 2017 , we disposed of five multifamily properties totaling 1760 units and four land parcels totaling approximately 23 acres . development as another part of our growth strategy , we invest in a limited number of development projects . development activities may be conducted through wholly-owned affiliated companies or through joint ventures with unaffiliated parties . fixed price construction contracts are signed with unrelated parties to minimize construction risk . we typically manage the leasing portion of the project as units become available for lease . we may also engage in limited expansion development opportunities on existing communities in which we typically serve as the developer . while we seek opportunistic new development investments offering attractive long-term investment returns , we intend to maintain a total development commitment that we consider modest in relation to our total balance sheet and investment portfolio . during the year ended december 31 , 2017 , we incurred $ 170.1 million in development costs and completed 7 development projects. .