Lave March Chapter 7 Diffusion 12 3 12 Diffusion spreading out Can diffuse a fact or belief or an attitude or behavior or opinions Big target audience Everett M Rogers Diffusion of Innovations Spreading information About health promoting behaviors condoms About risks o Texting and driving About dangerous products or recalls About your political candidate About your commercial product o Viral marketing either in person or on internet xMore topics Blogs linking blogs Rumors gossip Agricultural innovations o Fertilizer o Care of land Early adopters and opinion leaders Basic Assumptions For diffusion to occur people must be connected by a communication link o May be symmetrical or asymmetrical o May be present absent or probable For diffusion to occur the object of diffusion must be transmitted by the party who has it For diffusion to occur the transmission must be accepted by the party who doesn t already have the object of diffusion At any point in time every party either has the object of diffusion Once a party has the object s he never loses it or does not Summary Contact Transmission Acceptance You have it or you do not You never lose it Divorce Modeling intergenerational diffusion o How children catch divorce from their parents is roughly the idea o This is a bad way to express it because it seems to blame parents for their children s actions o Book is copyrighted in 1975 Divorce 4 types of couples o I Parents of both H W are divorced o II Parents of H divorced but not those of W o III Parents of W divorced but not those of H o IV Parents of neither H nor W divorced If divorce is contagious rates should be To simplify things initially I II III IV o Assume all children marry within their generation o Assume each type of couple has same number of kids o Assume that males females 50 o Assume that marriage pairings are random o Assume the initial rate of divorce is 20 So if the divorce rate is 20 in generation 1 then o 20 of H come from divorced parents o 20 of W come from divorced parents So of the 20 of H with divorced parents 20 of them will marry W with divorced parents Generation 2 looks like o I All parents divorced 4 20 x 20 o II H parents divorced 16 20 x 80 o III W parents divorced 16 80 x 20 o IV Neither divorced 64 80 x 80 Have to add up to 1 o 100 with both divorced parents divorce o 40 with one divorced parent divorces o 0 with no divorced parents divorces Add in some contagion assumptions how infectious divorce is One of your best friends got married You won t know this unless you were told by those who have known This is based on the second assumption that for diffusion to take place the object of diffusion must be transmitted by the person who already has it o Yes Divorce Can continue this sort of analysis to the next generation After 5 generations get table p 357 Algebra supplied p 358 Steady State Equilibrium Same divorce rate from one generation to another Algebra p 359 leads to these possibilities o D rate is zero o D rate is 100 o A is 50 Furthermore o If a 50 D rate approaches 0 o If a 50 D rate approaches 100 Epidemiology Two key questions o What is the rate of diffusion o What is the pattern of diffusion Mostly just have models of the rate though 12 5 12 Model of Information Explosion Birth Model Problem is diffusion of info about new boss Assumptions don t have it o Everyone who hears it believes it First Results At first Carter knows Hour 1 Carter tells A B C total 4 Hour 2 each of the 4 tells 3 people total 4 4x3 16 Rate is delta n delta t where n is the number of people N at start New delta n delta t total at end Limits o Each hour every person who has the info tells 3 people who The analysis so far birth model would lead to more people knowing the information than there are people Various sorts of things limit the diffusion process For ex as diffusion continues it becomes harder to find someone who doesn t already know Birth Model with Limits Taking the growth limit eg number of people in the organization into account N growth limit n number who have the info at the start of the time period t time period a diffusion rate o Delta n delta t a n N n o This is the term that puts a limit on the whole equation NB really only n is changing through the diffusion process Limits Delta n delta t a n N n Common sense observations o N will be larger than n until they are equal o The a n term will be small at first o The N n term will be large at first o Equation is a times number who know it time the number who don t than 1 N To guarantee that n delta n can t exceed N a can t be greater A worked ex p 373 The graph p 374 called an ogive ohjive it looks like a flat S number of people who know is vertical time is horizontal axis o Growth in number who know accelerates with the fastest growth where half of them know o Flattens out at end when targets are rare o The number of people who have yet to acquire the diffusion What happens to N n during the course of the diffusion process N n object o Shrinks Broadcast Diffusion Person to person contact up to now But can also broadcast information eg through mass media Let s work with the ex of a radio station and assume that the info only comes from the station ie no interpersonal relaying The Radio Station Assumptions o Total audience is 100 000 N o At a given hour only 10 tuned in a o The 10 are randomly distributed Delta n delta t a N n o As you go through broadcast day number of targets shrink listenership has object of diffusion o More effectively you diffuse faster this will happen o Watch results and decide Diffusion for Radio Station Graph of diffusion p 378 Shape is sort of gentle upward curve bowed a little toward upper Almost linear but will obviously flatten when it gets close to left hand corner 100 000 N Three Diffusion Models Graphs p 379 study carefully Birth process No limits What affects a a is the diffusion coefficient Exposure o Easy simple rumors will have higher a than complex o The easier exposure is the higher a will be Transmission ease materials Acceptance o More important things will move faster o More credible source a will be higher Billboards sponsored ads on Facebook Diffusion and Adoption may still be slow Information can diffuse quickly yet adoption of the innovation o Text …