That's strange, looking at the TSP monthlies, S & I Fund was the place to be in Feb 2010 - 2012 while you were better off in G or F from 2006 - 2009. Here are the Feb monthlies I'm looking at:
[TD="bgcolor: #FFFF99, align: left"]Date[/TD]
[TD="bgcolor: #CCFFCC, align: left"]G Fund[/TD]
[TD="bgcolor: #CCFFCC, align: left"]F Fund[/TD]
[TD="bgcolor: #CCFFCC, align: left"]C Fund[/TD]
[TD="bgcolor: #CCFFCC, align: left"]S Fund[/TD]
[TD="bgcolor: #CCFFCC, align: left"]I Fund[/TD]
[TD="bgcolor: #FFFF99, align: right"]Feb-06[/TD]
[TD="align: right"]0.36%[/TD]
[TD="align: right"]0.28%[/TD]
[TD="align: right"]0.22%[/TD]
[TD="align: right"]
(0.98%)
[/TD]
[TD="align: right"]
(0.27%)
[/TD]
[TD="bgcolor: #FFFF99, align: right"]Feb-07[/TD]
[TD="align: right"]0.34%[/TD]
[TD="align: right"]1.53%[/TD]
[TD="align: right"]
(1.95%)
[/TD]
[TD="align: right"]
(0.26%)
[/TD]
[TD="align: right"]0.18%[/TD]
[TD="bgcolor: #FFFF99, align: right"]Feb-08[/TD]
[TD="align: right"]0.24%[/TD]
[TD="align: right"]0.16%[/TD]
[TD="align: right"]
(3.28%)
[/TD]
[TD="align: right"]
(2.05%)
[/TD]
[TD="align: right"]
(0.66%)
[/TD]
[TD="bgcolor: #FFFF99, align: right"]Feb-09[/TD]
[TD="align: right"]0.21%[/TD]
[TD="align: right"]
(0.39%)
[/TD]
[TD="align: right"]
(10.64%)
[/TD]
[TD="align: right"]
(10.22%)
[/TD]
[TD="align: right"]
(10.23%)
[/TD]
[TD="bgcolor: #FFFF99, align: right"]Feb-10[/TD]
[TD="align: right"]0.24%[/TD]
[TD="align: right"]0.38%[/TD]
[TD="align: right"]3.11%[/TD]
[TD="align: right"]4.89%[/TD]
[TD="align: right"]0.06%[/TD]
[TD="bgcolor: #FFFF99, align: right"]Feb-11[/TD]
[TD="align: right"]0.22%[/TD]
[TD="align: right"]0.26%[/TD]
[TD="align: right"]3.42%[/TD]
[TD="align: right"]4.52%[/TD]
[TD="align: right"]3.33%[/TD]
[TD="bgcolor: #FFFF99, align: right"]Feb-12[/TD]
[TD="align: right"]0.12%[/TD]
[TD="align: right"]0.05%[/TD]
[TD="align: right"]4.34%[/TD]
[TD="align: right"]3.99%[/TD]
[TD="align: right"]5.14% [/TD]