"shrink in size" is correct and usable in written English.
You could use it to describe a change in physical size, such as "The balloon began to shrink in size as the air leaked out of it."
As the Forces shrink in size, you're more likely to go.
"The technology continues to shrink in size and gets easier to use".
When humans descend to greater depths, the rising pressure forces the lungs to shrink in size.
A delta, in these circumstances, will begin to shrink in size (see river: Deltas).
If passed, such a requirement is likely to prompt the largest banks to shrink in size.
After menopause, the ovaries shrink in size and usually consist of old fibrous tissue.
It just started to taper off and shrink in size by the last quarter of the century".
[C11.] Combating Gadget Theft As gadgets shrink in size and grow in popularity, theft has grown, too.
While the electronic devices we use shrink in size, the information we create doubles every two years.
Likewise, when fat is utilized by the body, adipose cells shrink in size, as opposed to decreasing in number.
