Adsense are not filling all my inventory

[MissMandy]

For the first time ever Adsense are not filling all my inventory. I must admit my surprise on this, but have only just noticed it over the last few days. Anyone else having the same situation?

[Chris]

January is triple witching.

Year long campaigns expire
quarter long campaigns expire
month long campaigns expire

All ad networks get lower inventory in early january, it eventually bounces back - but of course it is off for adsense to be visually affected, sign of the times I guess.