Hey everyone,
I recently failed a case interview and tried the failed calculation again at home, but cannot figure it out (maybe I am overseeing an easy point).
So the task was to forecast the two sub-market sizes for the next year. We know that overall the market growth rate is +10% per year. However, the market has two sub-segments which are growing at different rates.
Subsegment A is 100 in year 1 and 120 in year 2 (growing faster than the overall market, +20%). Subsegment B is 100 in year 1 and 90 in year 2 (declining market, -10%).
How can I forecast year 3 of sub-segment A and B by taking into account the historic growth rate (A growing fast and B declining), but also achieving a total market growth of 10% (from 210 to 231)?
Thanks a lot :)
Year one: A = 100; B=100
Year two: A = 120 (growth of 20%); B=90 (decline of 10%)
Then year three: A=120*1.2 = 144; B=90*0.9=81. A + B = 225
However, the market has grown overall. So if you assume that both segments are equally impacted by this overall market growth, then you need to know what proportion of the new market they would have. This is where you calculate A's market share as 64% (144/225) and B's as 36% (81/225).
Then apply these percentages to the new total market of 231. So A's total value is 64%*231 = 148 and so on.
Does that make sense?
This is in contradiction to the initial condition that A is growing faster than the market and B is declining 10% -- I don't think it is necessary that both segments are equally impacted. However, that condition will a solution out of many different possible ones such as the one I have calculated below.
Let’s say that we’re talking about two burger stands in a football stadium. One sells vegan burgers (sub-segment A) and one sells meat burgers (sub-segment B).
It’s a small stadium and in year 1 there are 200 seats. The proportion of people eating meat and vegan burgers is equal - so 100 get a meat burger and 100 get a vegan one.
The next year they build a little extension and add 5% additional capacity - so 10 new seats, so the stadium can accommodate 210 people. The people who turn up are getting more environmentally conscious, so more opt for the vegan burger than the meat burger. Now 90 people go for the meat one (a 10% reduction) and 120 go for the vegan one (a 20% growth). If they hadn’t added the additional 10 seats then maybe 85 would have had meat (a 15% reduction) and 115 would have had vegan (a 15% growth), but they had the new people come in who pushed the figures up. But we don’t know what the switch would have been if we hadn’t had the capacity expansion.
In year 3 they add another 10% capacity, or 21 seats. So the question is - are all these new people vegans or do some eat meat?
This is why we need to know how the growth is split over the segments.
If they’re all vegans (sub-segment A) then your calculation is accurate - we’ll see a reduction in 10% of meat eaters as people make the switch from meat to vegan, and all the growth will be in vegan burgers. However, what if some of them are meat eaters?
Therefore the calculation I proposed assumed that the proportion of vegan to meat eaters in the new seats would mirror that of year 2. I hope that makes sense!