What might cause an empty pie shell to shrink excessively when baked?

An empty pie shell may shrink excessively when baked primarily due to insufficient gluten development. Gluten provides elasticity and structure to the dough, which is essential for maintaining the shape of the pie shell during the baking process. When the gluten is not developed adequately, the dough lacks the necessary strength to hold its shape, leading to a tendency to shrink or collapse as it bakes.

Inadequate gluten can result from using a flour with low protein content or not mixing the dough long enough to form the gluten network properly. This structural issue results in a pie shell that cannot withstand the heat of the oven, causing it to shrink as the moisture evaporates and the fat melts.

Other factors such as excess sugar, too much butter, and overmixing do impact the texture and integrity of the dough, but they do not primarily cause the excessive shrinking observed in an empty pie shell during baking.