Which competitive force impacted the printed encyclopedia industry significantly?

The significant impact on the printed encyclopedia industry primarily arose from the presence of substitute products or services. With the advent of digital technology, particularly the rise of the internet, alternative resources such as online databases and websites like Wikipedia emerged. These digital platforms provided similar information more conveniently and often at little to no cost, making them attractive substitutes for traditional printed encyclopedias.

As a result, consumers increasingly turned to these digital alternatives, leading to a decline in sales and relevance for printed encyclopedias. Unlike traditional forms that required substantial investment in physical production and distribution, these substitutes allowed for easy access to information and often featured continuously updated content. This shift exemplifies how the introduction of competitive substitutes can disrupt an established industry, forcing traditional businesses to adapt or face obsolescence.

In contrast, factors like positioning among competitors or customer bargaining power may contribute to the dynamics of an industry but did not play as pivotal a role in the decline of printed encyclopedias as the availability of substitute products. Likewise, while low cost of entry might affect new competitors entering the market, it doesn't encapsulate the core challenge the printed encyclopedia faced with the rise of digital services.