Why the external links decrease so many?

Last month,i saw the external links at google webmaster,it's 40 thousands,but last week,it has dereased to 20 thousands,and now it only have 10 thousnads,anyone can answer my question?

 

It seems today or yesterday updated.
my external links decrease 10%.
internal links decrease 40%

 

I big drop on mine too.... I lalso lost ranking for many keywords... don't know why?

 

I noticed the same thing for one or two of my sites - GW showed far fewer external links for some of my sites. However,, the count went back in the last few days.

 

I have also seen a very big drop in two of my websites, don't really know the real reason but it was updated two days ago !!

 

I have noticed the same thing as well I think this occurs when google is making
some type of changes to their algorithm.

 

I think dropped your links.