In the United Kingdom during the 50's and 60's the major record companies had so much power that indie labels struggled
Oh yeah? That sounds awful.
Many British producers and artists launched indie labels as outlets for their work but most were swallowed up by the major labels.
In the United States, independent labels and distributors often banded together to form organizations to promote trade and parity within the industry.
Yes, and in the 1980's Alternative rock emerged from the indie music underground and then became popular in the 90's.
The 1990's brought Affiliated Independent Record Companies (AIRCO)
In the 2000's, as a result of changes in the music industry, indie rock acts started gaining success making people wonder about its meaningfulness as a term.
Many acts choose to go from an independent label to a major label if given the opportunity as major labels have considerably more power and financial means to promote and distribute product
One of the labels in the early 2000's was Nothing Records.  An American record label specializing in industrial rock and electronic music.
Major label advances are generally much larger than independent labels can offer.