"proportion varied" can be used in written English and is grammatically correct.
It is often used to express that a ratio or percentage has changed or is different from what was initially expected or assumed. Example: The country's economic growth has been sluggish, with the proportion of GDP spent on healthcare remaining relatively constant, while the proportion varied significantly for education and defense.
FRANK: The proportion varied.
The proportion varied according to state, from 8% in Victoria up to 86% in the Northern Territory.
This proportion varied substantially across the 25 different population subgroups identified.
A study published in 1959 reported that the seizures were severe; from half to all of the men affected — the proportion varied in different programs — went into convulsions, and several died.
The coatings comprised a mixture of TiCxN1 − x, Ag and a-C(N x phases whose relative proportion varied depending on the Ag/Ti ratio.
Temporally, the macrophyte proportion varied during the hydrological year, with a clear increment from late spring to early autumn (i.e. vegetation cover reached 40%, on average, of the channel surface).
The proportion varied by health authority from 0.007% to 56.5%.
Agreement using Cohen's kappa; multivariate logistic regression.The proportion varied substantially among the data sources.
Consistent with previous studies, a small proportion of airborne fibres were longer than >5 microm in length, but the proportion varied considerably by plant operation (range 6.9%too 20.8%).
Over this period, the average self-employment rate was at 11.5%% of total employment and this large proportion is not unique to the UK: across all OECD countries this proportion varied from 8 to 30%% (Blanchflower 2004).
TEM results for 77 airborne dust samples found that only a small proportion of airborne fibres were measured by PCM (>0.25 microm in diameter and >5 microm in length) and the proportion varied considerably by plant and operation (range 2.9%too 10.0%).
