"indicator of the extent" is grammatically correct and can be used in written English.
You can use it when you want to describe something that shows the degree or level of something. Example: The rising number of COVID-19 cases in the country is a clear indicator of the extent of the pandemic's impact on the population.
The damage index is an indicator of the extent of strain energy stored in the rotational spring.
A possible indicator of the extent of degradation is the organic fraction of solids in the effluent.
Both Republicans and Democrats said that for many voters, the course Mr. Bush charts would be interpreted as a indicator of the extent to which he feels bound to the right or, alternately, is willing to reach toward the center.
HRW added that it "could severely restrict the freedom of assembly of political parties and nongovernmental groups" and was "an important indicator of the extent to which the new government is going to allow for political space in Egypt".
This sequence has not been reported before and it is used in this study as a qualitative indicator of the extent of silver corrosion.
A computerised lexical decision task assessed participants' subsequent reaction times to message words, as an indicator of the extent of processing of the previously viewed message.
They provide yet another indicator of the extent to which Pakistani militants are working to shape the outcome of the Afghan war as the July 2011 deadline approaches to begin withdrawing American troops.
Response surface methodology was used to evaluate the effects of the processing parameters of TAMD on the final dry solids content, which is a fundamental dewatering parameter and an excellent indicator of the extent of TAMD.
A response surface methodology (RSM) was used to evaluate the effects of the processing parameters of IXED on (i) the abatement yield of the metal cation, which is a fundamental purification parameter and an excellent indicator of the extent of IXED, (ii) the current yield or the efficiency of copper transport induced by the electrical field and (iii) the energy consumption.
Our results show that this method for mapping the extent and mass-excess of lower-crustal magmatic products provides an effective indicator of the extent and intensity of magmatism during LIP events, and that this can help understand LIP processes, including ore-deposit formation.
A response surface methodology (RSM) was used to evaluate the effects of the processing parameters of EDW on (i) the final dry solids content, which is a fundamental dewatering parameter and an excellent indicator of the extent of EDW and (ii) the energy consumption calculated for each additional mass of water removed.
