future minimum lease commitments for office premises and equipment under non-cancelable leases , along with minimum sublease rental income to be received under non-cancelable subleases , are as follows : period rent obligations sublease rental income net rent .
guarantees we have certain contingent obligations under guarantees of certain of our subsidiaries ( 201cparent company guarantees 201d ) relating principally to credit facilities , guarantees of certain media payables and operating leases . the amount of such parent company guarantees was $ 327.1 and $ 327.9 as of december 31 , 2007 and 2006 , respectively . in the event of non-payment by the applicable subsidiary of the obligations covered by a guarantee , we would be obligated to pay the amounts covered by that guarantee . as of december 31 , 2007 , there are no material assets pledged as security for such parent company guarantees . contingent acquisition obligations we have structured certain acquisitions with additional contingent purchase price obligations in order to reduce the potential risk associated with negative future performance of the acquired entity . in addition , we have entered into agreements that may require us to purchase additional equity interests in certain consolidated and unconsolidated subsidiaries . the amounts relating to these transactions are based on estimates of the future financial performance of the acquired entity , the timing of the exercise of these rights , changes in foreign currency exchange rates and other factors . we have not recorded a liability for these items since the definitive amounts payable are not determinable or distributable . when the contingent acquisition obligations have been met and consideration is determinable and distributable , we record the fair value of this consideration as an additional cost of the acquired entity . however , we recognize deferred payments and purchases of additional interests after the effective date of purchase that are contingent upon the future employment of owners as compensation expense . compensation expense is determined based on the terms and conditions of the respective acquisition agreements and employment terms of the former owners of the acquired businesses . this future expense will not be allocated to the assets and liabilities acquired and is amortized over the required employment terms of the former owners . the following table details the estimated liability with respect to our contingent acquisition obligations and the estimated amount that would be paid under the options , in the event of exercise at the earliest exercise date . all payments are contingent upon achieving projected operating performance targets and satisfying other notes to consolidated financial statements 2014 ( continued ) ( amounts in millions , except per share amounts ) .
Period Rent Obligations Sublease Rental Income Net Rent
2008 $323.9 $(40.9) $283.0
2009 300.9 (37.5) 263.4
2010 267.7 (31.0) 236.7
2011 233.7 (25.7) 208.0
2012 197.9 (20.2) 177.7
2013 and thereafter 871.0 (33.1) 837.9
Total $2,195.1 $(188.4) $2,006.7
period rent obligations sublease rental income net rent
2008 $ 323.9 $ -40.9 ( 40.9 ) $ 283.0
2009 300.9 -37.5 ( 37.5 ) 263.4
2010 267.7 -31.0 ( 31.0 ) 236.7
2011 233.7 -25.7 ( 25.7 ) 208.0
2012 197.9 -20.2 ( 20.2 ) 177.7
2013 and thereafter 871.0 -33.1 ( 33.1 ) 837.9
total $ 2195.1 $ -188.4 ( 188.4 ) $ 2006.7