When jeans are patterned, why do they deviate from the size of pants?

There are several reasons why the mode does not discharge; 1。 When making a pattern according to the sample pants, it should be noted that the bought pants are modified many times before making a pattern. 2。 In the production process, it is different from the original pattern after the process of drawing back. 3。 Jeans generally need washing water, and the shrinkage is put in when making samples. 4。 It also has something to do with fabrics. When ready-made, some fabrics will become bigger and some will become smaller. Adjust the pattern according to the sample.