36 duke realty corporation annual report 2013 leasing/capital costs tenant improvements and lease-related costs pertaining to our initial leasing of newly completed space , or vacant space in acquired properties , are referred to as first generation expenditures . such first generation expenditures for tenant improvements are included within "development of real estate investments" in our consolidated statements of cash flows , while such expenditures for lease-related costs are included within "other deferred leasing costs." cash expenditures related to the construction of a building's shell , as well as the associated site improvements , are also included within "development of real estate investments" in our consolidated statements of cash flows . tenant improvements and leasing costs to re-let rental space that we previously leased to tenants are referred to as second generation expenditures . building improvements that are not specific to any tenant but serve to improve integral components of our real estate properties are also second generation expenditures . one of our principal uses of our liquidity is to fund the second generation leasing/capital expenditures of our real estate investments . the following table summarizes our second generation capital expenditures by type of expenditure ( in thousands ) : .
what was the average cash outflows for real estate development investments from 2011 to 2013
second generation tenant improvements and leasing costs increased due to a shift in industrial leasing volume from renewal leases to second generation leases ( see data in the key performance indicators section of management's discussion and analysis of financial condition and results of operations ) , which are generally more capital intensive . additionally , although the overall renewal volume was lower , renewals for office leases , which are generally more capital intensive than industrial leases , increased from 2012 . during 2013 , we increased our investment across all product types in non-tenant specific building improvements . the increase in capital expenditures for the development of real estate investments was the result of our increased focus on wholly owned development projects . we had wholly owned properties under development with an expected cost of $ 572.6 million at december 31 , 2013 , compared to projects with an expected cost of $ 468.8 million and $ 124.2 million at december 31 , 2012 and 2011 , respectively . cash outflows for real estate development investments were $ 427.4 million , $ 264.8 million and $ 162.1 million for december 31 , 2013 , 2012 and 2011 , respectively . we capitalized $ 31.3 million , $ 30.4 million and $ 25.3 million of overhead costs related to leasing activities , including both first and second generation leases , during the years ended december 31 , 2013 , 2012 and 2011 , respectively . we capitalized $ 27.1 million , $ 20.0 million and $ 10.4 million of overhead costs related to development activities , including construction , development and tenant improvement projects on first and second generation space , during the years ended december 31 , 2013 , 2012 and 2011 , respectively . combined overhead costs capitalized to leasing and development totaled 35.7% ( 35.7 % ) , 31.1% ( 31.1 % ) and 20.6% ( 20.6 % ) of our overall pool of overhead costs at december 31 , 2013 , 2012 and 2011 , respectively . further discussion of the capitalization of overhead costs can be found herein , in the discussion of general and administrative expenses in the comparison sections of management's discussion and analysis of financial condition and results of operations. .