"shrink to half" is correct and usable in written English.
For example, you can use it to describe the size of something that has become smaller, such as: "The population of the town shrank to half its original size."
After that, she put her hands in her lap, became very quiet, and seemed to shrink to half her size.
He said: "It was on Labour's watch that British manufacturing was abandoned and left to shrink to half its size.
He considers the prediction that the airline industry will shrink to half a dozen big carriers as an "overstatement," but he does expect small "marginal" carriers to soon run into more difficulty.
Your lungs suddenly shrink to half the size and can barely hold enough oxygen to keep you conscious.
For example, Easton Glacier in Washington state, U.S. will likely shrink to half its size but at a slowing rate of reduction and stabilize at that size despite the warmer temperature over a few decades.
By 1938 the number had shrunk to half.
Despite its market-beating streak, the fund has shrunk to half its peak size because of big losses for nearly three years.
Because of warmer temperatures attributed to climate change, Thorthormi lake has nearly tripled in size since 2001, to 3.42 square kilometers, or 1.32 square miles, while the natural moraine dam of rocks containing it has shrunk to half its height, according to the environmental group W.W.F.
Then the TCP congestion window shrinks to half of congestion window size of steady state.
"The town has 7,000 people, and it shrinks to half that when school's out," he said.
The ensuing chaos undermined the economy, which shrank to half the size it had been in 1980.
