ION GEOPHYSICAL CORP

CUSIP: 462044108 Class: COM

CALIFORNIA STATE TEACHERS RETIREMENT SYSTEM's Holding History (CIK: 0001081019)

Note: Option positions (PUT/CALL) are excluded.

Q4 2015
Shares 261,518 Value ($000) $132 Avg Close — Range —
Q3 2015
Shares 256,792 Value ($000) $100 Avg Close — Range —
Q2 2015
Shares 257,692 Value ($000) $276 Avg Close — Range —
Q1 2015
Shares 234,890 Value ($000) $510 Avg Close — Range —
Q4 2014
Shares 239,590 Value ($000) $659 Avg Close — Range —
Q3 2014
Shares 238,571 Value ($000) $666 Avg Close — Range —
Q2 2014
Shares 235,917 Value ($000) $996 Avg Close — Range —
Q1 2014
Shares 242,017 Value ($000) $1,019 Avg Close — Range —
Q4 2013
Shares 240,617 Value ($000) $794 Avg Close — Range —
Q3 2013
Shares 239,417 Value ($000) $1,245 Avg Close — Range —
Q2 2013
Shares 232,043 Value ($000) $1,397 Avg Close — Range —
Q1 2013
Shares 229,394 Value ($000) $1,562 Avg Close — Range —