Madame Double Breasted Wool & Cashmere Belted Coat

I've had this coat for years, had to move the buttons slightly as my body changed, and I love it so much that I decided to buy a new one in the bigger size (US 12). And to my surprise, there's 1 (!!, seriously ONE) cm difference in the hip area between both sizes. The top is bigger, yes, but the waist and hip are basically the same. Had to move the buttons again :-) Once the buttons are moved, it's a perfect fit, and I've worn the coat almost every day, but I seriously do not understand how those coats are made. Be aware that if you have any female attributes at all, the coat might be too restrictive in the hip area and the buttons will have to be moved. BTW, even the largest size available differs by only about 4 cm around the hip from US 8 or 10. So without moving the buttons there will simply be no perfect size for an average human body.