I will preface this by saying that I have at least ten pairs of Birkenstocks and have worn them comfortably for years.  But I am in severe pain when I wear the ones that were manufactured recently.  I was going to doctors and thinking I needed surgery.  Then, I found an OLD pair of Birkenstocks that I had bought on sale years ago and was saving until my dark brown ones wore out.  When I put them on, instant relief.  This proves that Birkenstocks are not the same as they used to be.  Now, I cannot wear them at all and am hard pressed to find a replacement.  It seems that everything that used to be good is now awful, due to the corporations outsourcing and putting profit before quality.  This has also happened with Ecco and New Balance.  I don't even know what to buy that will be comfortable and of good quality.  But I can say with certainly that I will not be buying any more Birkenstocks.  And I think I deserve a refund for the five or so pairs that I bought before I realized what was going on.