A phrase that is commonly used in the United Kingdom
to mean earnings from services, which are “invisible,” in contrast to physical
goods or manufactured products that are “visible.”
"invisible earnings." YourDictionary, n.d. Web. 17 May 2018. <http://www.yourdictionary.com/invisible-earnings>.
invisible earnings. (n.d.). Retrieved May 17th, 2018, from http://www.yourdictionary.com/invisible-earnings