The Economy of Words: The art of communication using all symbolic measures afforded by technology. Or, how to communicate effectively and participate in the information economy.
As it is the case in finance, using this economy of words wisely means to reap maximum benefits with minimal input. If you could drive your point home in, let's say one concise sentence instead of a wordy paragraph, you've put the economy of words to good use.
According to the Chinese saying: a picture says more than a thousand words. Translating a picture to words, might not have the same effect, hence the economy of words may not have been put to good use.
I hope this helps.