How to Model Viral Growth
Author
Walkthrough
Rahul Vohra
http://www.linkedin.com/today/post/article/20121002124206-18876785-how-to-model-vira
Contact
rahul@vohra.org.uk
www.linkedin.com/in/rahulvohra
www.facebook.com/rahul.vohra
www.twitter.com/rahulvohra
24206-18876785-how-to-model-viral-growth-the-hybrid-model
The Simplest Possible Model
Variables
Intial users
Viral factor
5,000
0.2
7,000
6,000
Output
Month
1
2
3
4
5
6
7
8
9
10
11
12
Users (month start)
Growth
5,000
6,000
6,200
6,240
6,248
6,250
6,250
6,250
6,250
6,250
6,250
6,250
1,000
200
40
8
2
0
0
0
0
0
0
0
5,000
4,000
3,000
2,000
1,000
Users (month start)
7
Month
10
11
12
The Hybrid Model
Variables
Launch press
70,000
App store search growth
App store downloads / month
% who activate
App store search growth / month
40,000
60%
24,000
Direct traffic growth
Direct traffic downloads / month
% who activate
Direct traffic growth / month
10,000
60%
6,000
Viral factor
0.2
Output
Month
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Users (month start) Launch press App store
104,000
158,800
203,760
246,752
289,350
331,870
374,374
416,875
459,375
501,875
544,375
586,875
629,375
671,875
714,375
756,875
799,375
70,000
-
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
19
20
21
22
23
24
841,875
884,375
926,875
969,375
1,011,875
1,054,375
24,000
24,000
24,000
24,000
24,000
24,000
Users (mo
600,000
500,000
400,000
300,000
200,000
100,000
Direct traffic Viral growth Total growth
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
20,800
10,960
8,992
8,598
8,520
8,504
8,501
8,500
8,500
8,500
8,500
8,500
8,500
8,500
8,500
8,500
8,500
104,000
54,800
44,960
42,992
42,598
42,520
42,504
42,501
42,500
42,500
42,500
42,500
42,500
42,500
42,500
42,500
42,500
42,500
10,000
10,000
10,000
10,000
10,000
10,000
8,500
8,500
8,500
8,500
8,500
8,500
42,500
42,500
42,500
42,500
42,500
42,500
Users (month start)
7
Month
10
11
12
Virality as the Amplification Factor
Amplification factor, a
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
0.95
0.98
0.99
1.00
1.11
1.25
1.43
1.67
2.00
2.50
3.33
5.00
10.00
20.00
40.00
100.00
Amplification F
10.00
9.00
8.00
7.00
Amplification Factor
Viral factor, v
6.00
5.00
4.00
3.00
2.00
a = 1.25
1.00
-
0.10
0.20
Amplification Factor vs. Viral Factor
a = 3.33
a = 1.67
a = 1.25
0.20
0.30
0.40
0.50
Viral Factor
0.60
0.70
0.80
0.90
1.00
The Hybrid Model, with Simple Loss
Variables
300,000
Launch press
70,000
250,000
App store search growth
App store downloads / month
% who activate
App store search growth / month
40,000
60%
24,000
Direct traffic growth
Direct traffic downloads / month
% who activate
Direct traffic growth / month
10,000
60%
6,000
Viral factor
200,000
150,000
100,000
50,000
0.2
% of users lost / month
15%
Output
Month
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Users (month start) Launch press App store
104,000
143,200
166,680
184,670
199,568
212,152
222,833
231,909
239,623
246,180
251,753
256,490
260,516
263,939
70,000
-
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
16
17
18
19
20
21
22
23
24
266,848
269,321
271,423
273,209
274,728
276,019
277,116
278,049
278,841
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
Users (month start)
10
Month
Direct traffic Viral growth Gross growth
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
20,800
10,960
8,992
8,598
8,520
8,504
8,501
8,500
8,500
8,500
8,500
8,500
8,500
8,500
104,000
54,800
44,960
42,992
42,598
42,520
42,504
42,501
42,500
42,500
42,500
42,500
42,500
42,500
42,500
Loss
Net growth
(15,600)
(21,480)
(25,002)
(27,701)
(29,935)
(31,823)
(33,425)
(34,786)
(35,943)
(36,927)
(37,763)
(38,473)
(39,077)
(39,591)
104,000
39,200
23,480
17,990
14,898
12,584
10,681
9,076
7,714
6,557
5,573
4,737
4,027
3,423
2,909
11
12
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
8,500
8,500
8,500
8,500
8,500
8,500
8,500
8,500
8,500
42,500
42,500
42,500
42,500
42,500
42,500
42,500
42,500
42,500
(40,027)
(40,398)
(40,713)
(40,981)
(41,209)
(41,403)
(41,567)
(41,707)
(41,826)
2,473
2,102
1,787
1,519
1,291
1,097
933
793
674
The Retention Curve
Week
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
Retention
81%
74%
82%
65%
64%
62%
58%
53%
58%
54%
54%
55%
47%
47%
43%
48%
49%
48%
49%
49%
45%
45%
44%
39%
39%
38%
39%
40%
41%
42%
45%
40%
42%
37%
38%
40%
Example Retention Cu
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0
12
16
Weeks since user was acqui
ple Retention Curve
20
Weeks since user was acquired
24
28
32
36
The Virality Curve
1
2
3
4
5
6
Viral Factor
0.2
0.1
0.05
0.025
0.0125
0.00625
Example Virality Cur
0.25
0.2
Viral Factor
Month
0.15
0.1
0.05
0
1
Month since user was acq
mple Virality Curve
4
Month since user was acquired
The Hybrid Model, with Retention and Virality Curves
Variables
Launch press
70,000
App store search growth
App store downloads / month
% who activate
App store search growth / week
40,000
60%
24,000
Direct traffic growth
Direct traffic downloads / week
% who activate
Direct traffic growth / week
10,000
60%
6,000
Users (m
300,000
250,000
200,000
150,000
Virality
Viral factor decay
Viral factor month 1
Viral factor month 2
Viral factor month 3
Viral factor month 4
Viral factor month 5
Viral factor month 6
Lifetime viral factor
0.50
0.20
0.10
0.05
0.03
0.01
0.01
0.39
100,000
50,000
Retention
Retention month 0 -> 1
Retention month 0 -> 2
Retention month 0 -> 3
Retention month 0 -> 4
Retention month 0 -> 5
Retention month 0 -> 6
65%
55%
51%
48%
44%
40%
Output
Month
-4
-3
Users (month start) Launch press App store Direct traffic
-2
-1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
67,600
88,088
109,269
128,407
145,638
161,061
178,637
196,206
213,814
231,445
249,092
266,750
284,417
302,087
319,758
337,430
355,103
372,775
390,448
408,121
425,794
443,467
461,141
70,000
-
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
24,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
Users (month start)
Growth Channels a
80,000
60,000
40,000
20,000
(20,000)
(40,000)
(60,000)
4
10
11
12
Month
Viral growth Gross growth Loss
Launch press
Net growth
App store
13,520
11,898
11,245
10,859
10,629
10,493
10,295
10,244
10,217
10,201
10,193
10,188
10,185
10,184
10,184
10,183
10,183
10,183
10,183
10,183
10,183
10,183
10,183
104,000
47,520
45,898
45,245
44,859
44,629
44,493
44,295
44,244
44,217
44,201
44,193
44,188
44,185
44,184
44,184
44,183
44,183
44,183
44,183
44,183
44,183
44,183
44,183
(36,400)
(27,032)
(24,716)
(26,108)
(27,628)
(29,206)
(26,918)
(26,726)
(26,636)
(26,586)
(26,554)
(26,534)
(26,521)
(26,516)
(26,513)
(26,511)
(26,511)
(26,510)
(26,510)
(26,510)
(26,510)
(26,510)
(26,510)
(26,510)
67,600
20,488
21,181
19,138
17,231
15,423
17,576
17,569
17,608
17,631
17,647
17,658
17,667
17,670
17,671
17,672
17,673
17,673
17,673
17,673
17,673
17,673
17,673
17,673
owth Channels and User Loss
10
11
Month
App store
Direct traffic
Viral growth
Loss
12
