15% Principle

[Roughly speaking] 上漲15% 就賣出手中 15% 的持股
再上漲15% 就再賣出目前手中 30% 的持股

[Q] 選定時間點 忘掉成本? 未考慮時間長度, as short as possible?
[Q] 針對單一個股?
[Q] 成本不是重點 重點在交易 在交易中產生現金的流動?

[Furthrer Investigating]
initial time= t;
initial price= p;
initial stocks quantity= Q;
initial value V= pQ

at time t1:
p1=1.15p, Q1=0.85Q, sell=0.15Q
V1= 0.15Q*p1 + p1*Q1= p1*Q
cash= C1= 0.15Q*p1=

at time t2:
p2= 1.3p, Q2= 0.7Q1 =0.595Q, sell= 0.3Q1= 0.255Q
V2= 1.3P*Q1 + C1
C2=C1 + 1.3p *0.3Q1 = C1 + ...