Have speakers really improved within the last 20 years??


Question:

  • If there is one measurement that would prove that speakers have indeed got better over the last 20 years, what would it be? 

I dont just want one example of a speaker from today that has a better measurement than another speaker from 20 years ago because that could just be a coincidence. I want to see IRREFUTABLE PROOF that most speakers today have a measured performance in at least one area that is better than most speakers 20 years ago.

When I look at a typical bookshelf speaker from 20 years ago versus one from today i see little difference. All i see is a wooden box, typically mdf with a pair of drivers in 'em. There would be a small crossover circuit inside and a bit of foam inside the box and that would be the end of the story. I would like to believe that speakers have gotten better but I see no reason to believe it. All I see is that speakers may have gotten brighter and brighter with time to dupe us into thinking we are hearing more detail. 

This challenge is open to any audiophile or speaker designer reading this.
kenjit
How many ways can you possibly beat this dead horse.  What was once a forum with interesting and educating posts is now a car full of clowns heading to the circus....
do not recall seeing any graphs of FR from speakers over the years showing that it has become more flat
You're not looking at the right speakers. I'm not giving the answer,  your quest for the holy grail of speakers is for you to solve. 
They are better because I say so, and since I am the only measurement and judgement that matters, this case is closed.
That is the wrong answer to my question. The challenge is to provide a measurement that proves that speakers have gotten better with time. Your opinion is NOT a measurement. I dont want opinions I want measurements. 
Post removed 
@djones51  I asked what you mean when you say FR has gotten better? what is your definition of better FR?
You're not looking at the right speakers.
Which ones have you looked at? Name them
your quest for the holy grail of speakers is for you to solve.
No its not. The holy grail of every audiophile is BETTER SOUND QUALITY. 
Every audiophile should be equally concerned about this.  If there is no proof that speakers are getting better then its nothing more than make believe and we are not making progress. What would be the point of that?