When a security is delisted and then begins trading again at a later date, does CRSP pick it up again or is it lost forever?

If an issue leaves an exchange that is covered by CRSP (NYSE, Amex, or NASDAQ) and later returns, the gap is marked in the Name History Array with an Exchange Code of 0. During this time, event data is not tracked and time series data is filled in with missing values.

CRSP will resume coverage of the security if it has primary listing on NYSE, Amex, or NASDAQ and otherwise fulfills our universe requirements for the stock database.  New PERMNO or PERMCO may be assigned, depending on events that took place during the off-CRSP period.

EXAMPLE:

PERMNO 83404

Namedt        Enddt          Cusip            Ticker    Company Name             CLS    SH     Ex         SIC
19960430    19990616    71892810    PHYX   PHYSIOMETRIX INC        11                 3         3840
19990617    20000611    71892810                  PHYSIOMETRIX INC       11                 0         3840
20000612    20010823    71892810    PHYX   PHYSIOMETRIX INC        11                 3         3840
20010824    20050729    71892810    PHYX   PHYSIOMETRIX INC        11                 3         3840

This security ceased trading on NASDAQ on June 16, 1999.  It resumed trading on NASDAQ on June 12, 2000.  The interval between these dates is represented by a name line with Exchange Code set to zero, and the Ticker field blank.