Goodman Property Trust's property portfolio has fallen 10 per cent in value in the past year to $1.5 billion, according to an independent revaluation.

The 10.2 per cent, or $168.9 million, fall in asset values included a $57 million devaluation last September.

The investment portfolio fell 8.9 per cent, and the value of development land fell 18.5 per cent.

The drop is expected to cut net tangible assets by about 13c a unit to about $1.04. Shares closed at a nine-year low of 80c.