Most TSP fund prices slipped last week as stocks gave back some of August’s earlier gains. The S Fund led the decline, the C and I Funds also finished lower, and the G Fund posted its usual small, steady gain. Here’s how each fund performed for the week of August 17–21, 2026.
Core Fund Performance
Fund
Weekly Return
G Fund
+0.09%
F Fund
-0.10%
C Fund
-1.39%
S Fund
-1.99%
I Fund
-0.08%
Lifecycle Fund Performance
Fund
Weekly Return
L Income
-0.23%
L 2030
-0.51%
L 2035
-0.65%
L 2040
-0.71%
L 2045
-0.77%
L 2050
-0.82%
L 2055
-1.00%
L 2060
-1.00%
L 2065
-1.00%
L 2070
-1.00%
L 2075
-1.00%
What Drove This Week’s Moves
Stocks lost ground during a choppy week, with Tuesday doing much of the early damage. The S Fund fell 1.64% that day, followed by another 1.17% decline on Thursday. Small- and mid-cap stocks bore the brunt of the selling, which is why the S Fund’s weekly loss of nearly 2% outpaced the C Fund’s 1.39% decline by a wide margin. The I Fund followed a similar path lower before recovering most of its losses on Friday, when it gained just over 1% to end the week down only 0.08%.
A Friday rebound across the stock funds kept the week from being worse: the C, S, and I Funds all posted gains on the final trading day, cutting into losses that had built up earlier in the week. The G Fund continued its steady, uninterrupted climb, and the Lifecycle Funds moved in line with their underlying stock exposure, with the more conservative L Income Fund losing just 0.23% while the longer-dated L Funds, which hold the most stock, each fell right around 1%.