Did you know that the whole business casual fashion was started by an oil crisis? It's true. Back in the 70's we went through one of the first real shortages of oil and OPEC became a household name. The government in part of its response to the shortage asked all businesses to up the thermostat setting in their air conditioned work spaces to cut down on electrical power and thereby save on oil that fired those electrical power plants.
You probably already know that a suit and tie are not really designed to be worn in an 80 degree environment. So the memo comes down from management basically saying that formal business attire is not required during the national air conditioning crisis and business casual was born as a fashion.
That memo back in the 70's typically defined business casual by defining what was not acceptable rather than what was. Pantyhose still had to be worn by women. Jeans, T shirts, sandals, shorts and basically anything that management deemed inappropriate was specifically banned. As a result, business casual meant no jacket and no tie for many men and it didn't mean much more for women.
When the crisis passed so did the business casual dress for everyday. Replacing it was "Casual Friday" a human resources gimmick to make everyone feel good about the company just before the weekend. And then something happened. The fashion industry smelled a new market and started promoting the idea that companies that were cutting edge and hip, like two new hot stocks Microsoft and Apple, understood the value of letting their employees have some freedom in dress rather than conforming to the company uniform.
Today 43% of all businesses have a casual dress code.
While each organization sets its own idea of what casual is, typically their policies include some common ground. The employment counseling office at American University defines business casual as half way between business formal and street wear. They give their graduates looking for a job this guidance on what is and isn't casual business.
For women it's a skirt or an informal dress so long as the length is appropriates (no minis). The skirt can be topped with a dress shirt, polo, sweater or sweater set. Pants are ok so long as they are full length and not made of denim. For men it's a collared shirt, casual slacks, a belt and shoes with socks. The shirt has to be tucked in and the pants can't be jeans.
Now understand that American University is located near Embassy Row in Washington DC so their idea of casual is just a tad more formal than say businesses in Los Angeles. The bottom line is the company sets the standard but in almost every case, regardless of the restrictions; working in casual dress is just so much more comfortable than a suit. Thank you OPEC.