The long skirts introduced in 1947 were looking too long by January of 1951. Compare this cranberry red coat dress, from November 1949 . . .
. . . with this fitted black coat from December, 1951.
The “One Yard Skirt,” Butterick 5087 from 1949 (below, left) was on the back cover of the November Butterick Fashion News flyer, and other skirts featured in that issue were as long, or longer.
Fourteen months later, Butterick showed these dresses with the title “Hemline Interest.”
There has certainly been a subtle change in proportions.
Other things that caught my eye are the hip-widening [or waist-narrowing] details on dress 5559 C (the bow) and 5564 (the full gathers below its fitted yoke.)
Suit 5083 has a “lumberjack top;” its waist-length jacket, tight around the waist, was often called an “Eisenhower” jacket in the fifties.
And the black, “bell-skirted” flared coat from December 1951 was designed to fit over very full skirts like these, held out by crinoline petticoats:
Often, a nylon crinoline would be built into a store-bought dress. Pattern companies depend on following trends, so shorter skirts must have been “in the air” before December of 1951. What-I-Found posted images from a Simplicity flyer, dated August 1950, here.