Understanding Society User Support

Hello
I'm using BHPS data and I merged xwavedat with xwaveid. Then I merged the resulting file with every wINDRESP file from a through r. In doing so, I used SPSS's "/in" command to mark whether a participant had data for a specific wave. Here is a snippet:

match files file = "c:\temp\tempx.sav"
/file = "c:\temp\tempxx.sav"
/file = "c:\temp\tempa.sav" /in=wave1
/file = "c:\temp\tempb.sav" /in=wave2
/file = "c:\temp\tempc.sav" /in=wave3
/file = "c:\temp\tempd.sav" /in=wave4

Wave1, Wave2, etc are dummy coded, so 1=yes. In theory, every participant should have had at least one wave of data. However, I only have wave-specific data for PIDs from 10002251 through 78133459. There is no wave-specific data for participants from 78133491 through 189364181, which is over half the dataset.

Are these UKPHS participants who have no BHPS data?

Thanks

Chris