What do you believe are the three most important changes in the American economy—positive or negative—over the last 100 years?

Google started as one of many internet search engines, amazon started as an online book seller, and ebay began as a site where people could sell used personal items in auctions. these firms have grown to be so large and dominant that they are facing antitrust scrutiny from competition regulators in the us and elsewhere. did these online giants grow by fairly beating competition, or did they use unfair advantages? are there any clouds on the horizon for these firms -- could they face diseconomies of scale or diseconomies of scope as they continue to grow? if so, what factors may limit their continued growth?

What is the sequence of events that could lead to trade surplus

Industrial engineers who specialize in ergonomics are concerned with designing workspace and devices operated by workers so as to achieve high productivity and comfort. a paper published in this research area reports on a study of preferred height for an experimental keyboard with large forearm-wrist support. a sample of 31 trained typists resulted in an average preferred height of 80.0 cm