Woven stretch fabrics are designed to provide both comfort and fit in clothing and other textiles. To achieve this, the fabric is manufactured to have a certain degree of stretch in a specific direction, typically horizontally. This is accomplished by shrinking the fabric in the stretch direction, wherein the spandex content exists, during the manufacturing process, which causes the fibers to become compact and creates a tension in the fabric that allows it to stretch.

The amount of shrinkage applied during the manufacturing process is a key factor in determining the stretch properties of a woven stretch fabric. The more the fabric is shrunk in the stretch direction, the greater the stretch potential of the fabric. However, increasing the lycra percentage in fabric does not directly increase the stretch. 

For example, increasing the content from 2% to 4%, might not increase the stretch in case the manufacturer does not shrink the fabric further in the stretch direction. Increasing the lycra content will only increase the fabric’s potential to further shrink in the stretch direction. However, if not further shrunk it will not by itself increase the stretch level.

Also, in most cases, manufacturers are offering stretch fabrics at higher width or lower stretch than the potential of that fabric. Hence, increasing lycra percentage in most cases will not yield a higher stretch in fabrics. However, shrinking fabrics further will in most cases increase the stretch level.  Hence, it is an incorrect notion that increasing lycra content increases stretch.

However, it is important to note that the type of yarn used and the construction of the fabric also play a role in determining the stretch properties of a woven stretch fabric. For example, using special types of spandex/lycra yarns can provide additional stretch or improve the performance of lycra. While, the type of weave used can impact the overall stretch potential of the fabric.

In addition, the finishing process can also affect the stretch properties of woven stretch fabrics. For example, applying heat or tension during the finishing process can change the amount of shrinkage and therefore impacting the stretch potential of the fabric.

In conclusion, the stretch properties of woven stretch fabrics are determined by a combination of factors, including the amount of shrinkage applied in the stretch direction, the type of yarn used, the construction of the fabric, and the finishing/heat-set process. By understanding these factors, you can choose the right woven stretch fabric for your specific needs and ensure that your finished product provides the desired level of stretch and comfort.