Can anyone tell me how it is possible for little trades to keep...

Can anyone tell me how it is possible for little trades to keep going through and effectively pulling the SP down. I will attempt to paste the last 10 trades for today as per my trading platform. Note the 4 digit trades, I would say the 5 digit trades are serious trades and the others? Any explanations gratefully received please??? JC
21-07-2008 03:34 PM $0.032 46593 $1,490.976
21-07-2008 02:23 PM $0.032 6195 $198.240
21-07-2008 02:23 PM $0.032 3211 $102.752
21-07-2008 02:23 PM $0.032 40351 $1,291.232
21-07-2008 02:16 PM $0.033 5281 $174.273
21-07-2008 02:16 PM $0.033 5281 $174.273
21-07-2008 01:54 PM $0.033 4548 $150.084
21-07-2008 01:24 PM $0.033 3233 $106.689
21-07-2008 12:29 PM $0.033 50000 $1,650.000
21-07-2008 12:25 PM $0.033 12381 $408.573