viral marketing Viral marketing is a business strategy that uses existing social networks to promote a product mainly on various social media platforms. Its name refers to how consumers spread information about a product with other people, much in the same way tha ...

, the K-factor can be used to describe the growth rate of websites, apps, or a customer base. The formula is roughly as follows: :

i=\text

(e.g. if each new customer invites five friends, ''i'' = 5) :

c=\text

(e.g. if one in five invitees convert to new users, ''c'' = .2) :

k = i * c

This usage is borrowed from the

basic reproduction number In epidemiology, the basic reproduction number, or basic reproductive number (sometimes called basic reproduction ratio or basic reproductive rate), denoted R_0 (pronounced ''R nought'' or ''R zero''), of an infection is the expected number of ...

in the medical field of

epidemiology Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population. It is a cornerstone of public health, and shapes policy decisions and evide ...

in which a virus having a k-factor of 1 is in a "steady" state of neither growth nor decline, while a k-factor greater than 1 indicates exponential growth and a k-factor less than 1 indicates exponential decline. In epidemiology, the k-factor is derived from the rates of distribution and infection for a disease. "Distribution" (

i

) measures the average number of people a host will contact while still infectious, and "infection" (

c

) measures how likely an average person is to also become infected after contact with an infectious host. In the context of viral marketing, a k-factor of less than 1 does not necessarily indicate that the product's userbase is declining overall. K-factor measures how effective word-of-mouth or member invitation schemes are, but there are other ways for a user to come to a new app. Social K-factor Defined With the advent of social media, a new evolution to the K-factor concept has emerged. The Social K-factor is an indicator of how viral a website is when content is shared from the website onto social media. It is a function of the Social Coefficient, which determines how fast content is spreading through social sharing, and the Sharing Ratio, a measure of how often your content is likely to be shared. As visitors to your website share your website's content on their social networks, the content can go viral because the social media posts attract new visitors who then share more content. The Social K-factor measures the lift delivered from social sharing.

References

Viral marketing {{marketing-stub