Assuming space is really expanding -
Due to expanding space, distant galaxies are supposed to be moving away from us.
When light leaves a distant galaxy, it's wavelength is red shifted to begin with due to doppler's effect.
But thereafter, the light keeps propagating through space which is continuously expanding. With expanding space, the red shift should keep on increasing for billions of years while it travels.
Therefore, the cumulative red shift must be much larger than what should be due to the doppler's effect at the onset.
Has this effect been taken into account when the calculations of rate of expansion of the universe are done?
Because, farther the source, more time the light has to travel through the expanding space, causing the red shift to be even greater.
Also, isn't it possible that some galaxies may be travelling towards us but because of cumulative red shift (due to expanding space), they appear to be moving away?
Same logic should apply to the gravitational waves, their frequency, wavelength, and amplitude.
Question is - does the cumulative red shift (due to travel through ever expanding space), make any sense? If so, has it been accounted for while doing calculations?