The phrase "third or more" is grammatically correct and can be used in written English.
Example: "Participants who completed the survey for the third or more time were excluded from the study."
"It is said that the shock is reduced by a third or more underground," he said.
"There was always a third or more left in the glass".
Some sellers have had to reduce prices by a third or more.
By 1351, a third or more of all Europeans were dead.
That's in stark contrast to the fall of a third or more at rival firms.
Region-wide crashes in 1997 and 2006 sent stock indices plummeting by a third or more.
Most independent analysts think the true fraction is a third or more.
According to council research, as many as a third or more of homes in some new developments are potentially vacant.
Ordinarily with stents, a third or more of the patients will develop scar tissue around the stent, obstructing the artery.
Ethnic Albanians make up perhaps a quarter, though some say a third or more, of Macedonia's two million people.
