"I get a competitive advantage when big tenants come in here," Malkin said, adding that average office rents in August 2006 were $26.50 per square foot, compared to the high $40s to high $50s nowadays.
 http://www.reuters.com/article/2012/05/06/us-usa-construction-retrofits-idUSBRE84505S20120506 

Average annual base rental payable according to SEC Filings by Empire State Building Associates L.L.C.
2011  $40 per square foot
2010   $31 per square foot
2009   $29 per square foot 
2008   $30 per square foot
2007    $35 per square foot 
2006    $34 per square foot
2005    $28.73 per square foot 
2004     $31.84 per square foot 
2003     $31.58 per square foot
2002     $31.46 per square foot
2001      $35.21 per square foot
2000      $35.26 per square foot
1999       $37.02 per square foot
1998       $33.85 per square foot
1997       $34 per square foot
1996       $29 per square foot

Sources:
2011

the average annual base rental payable  to Sublessee is approximately $40 per square foot (exclusive of electricity charges and escalation). The asking rents for new leases at the Building range from $38 to $53 per square foot.  
http://sec.gov/Archives/edgar/data/32776/000119312512159041/d329525d10k.htm 

2010
the average annual base rental payable to Sublessee is approximately $31 per square foot (exclusive of electricity charges and escalation). The asking rents for new leases at the Building range from $35 to $55 per square foot.
   http://sec.gov/Archives/edgar/data/32776/000003277611000014/esbacombinedb.htm 


2009
Pursuant to tenant space leases at the Building, the average annual base rental payable to Sublessee is approximately $29 per square foot (exclusive of electricity charges and escalation). The asking rents for new leases at the Building range from $32 to $52 per square foot. 
http://sec.gov/Archives/edgar/data/32776/000003277610000010/esba10kdoc.htm 

2008
the average annual base rental payable to Sublessee is approximately $30 per square foot (exclusive of electricity charges and escalation). The asking rents for new leases at the building range from $50 to $60 per square foot. 
http://sec.gov/Archives/edgar/data/32776/000003277609000011/esba10kkk.htm 

2007
the average annual base rental payable to Sublessee is approximately $35 per square foot (exclusive of electricity charges and escalation). The asking rents for the building range from $42 to $52 per square foot. http://sec.gov/Archives/edgar/data/32776/000003277608000019/empire10kcc.htm 

2006
average annual base rental payable to Sublessee is approximately $34 per square foot (exclusive of electricity charges and escalation). The asking rents for the building range from $42 to $52 per square foot.
http://sec.gov/Archives/edgar/data/32776/000003277607000011/empire10kccc.htm 

2005
average annual base rental payable to Sublessee is approximately $28.73 per square foot (exclusive of electricity charges and escalation). The asking rents for the building range from $35 to $41 per square foot. http://sec.gov/Archives/edgar/data/32776/000003277606000004/emp10k.htm 

2004
the average annual base rental payable to Sublessee is approximately $31.84 per square foot (exclusive of electricity charges and escalation). The asking rents for the building range from $33 to $37 per square foot. http://sec.gov/Archives/edgar/data/32776/000003277605000011/esbaamend.htm 

2003
the average annual base rental payable to Sublessee is approximately $31.58 per square foot (exclusive of electricity charges and escalation). The asking rents for the building range from $35 to $45 per square foot. http://sec.gov/Archives/edgar/data/32776/000003277604000007/ebsa.htm 


2002
the average annual base rental payable to Sublessee is approximately $31.46 per square foot (exclusive of electricity charges and escalation). The asking rents for the building range from $39 to $55 per square foot.
http://sec.gov/Archives/edgar/data/32776/000003277603000004/emoire10k.txt 

2001
the average annual base rental payable to Sublessee is approximately $35.21 per square foot (exclusive of electricity charges and escalation). The asking rents for the building range from $38 to $55 per square foot.
http://sec.gov/Archives/edgar/data/32776/000003277602000006/esba10k.txt 

2000
the average annual base rental payable to Sublessee is approximately $35.26 per square foot (exclusive of electricity charges and escalation). The asking rents for the building range from $39 to $55 per square foot.
http://sec.gov/Archives/edgar/data/32776/000003277601500007/empdocu.txt 

1999
the average annual base rental payable to Sublessee is approximately $37.02 per square foot (exclusive of electricity charges and escalation). The asking rents for the building range from $35 to $47 per square foot.
http://sec.gov/Archives/edgar/data/32776/0000032776-00-000012.txt 

1998
the average annual base rental payable to Sublessee is approximately $33.85 per square foot (exclusive of electricity charges and escalation)
http://sec.gov/Archives/edgar/data/32776/0000032776-99-000028.txt 

1997
the average annual base rental payable to Sublessee is approximately $34 per square foot (exclusive of electricity charges and escalation)
http://sec.gov/Archives/edgar/data/32776/0000032776-98-000002.txt 

1996
the average annual base rental payable to Sublessee is approximately $29 per square foot (exclusive of electricity charges and escalation)http://sec.gov/Archives/edgar/data/32776/0000032776-97-000005.txt