We consider robust one-way trading with limited information on price fluctuations. Our analysis finds the best guarantee of difference from the optimal offline performance. We provide closed-form solution, and reveal for the first time all possible worst-case scenarios. Numerical experiments show that our policy is more tolerant of information inaccuracy than Bayesian policies, and can earn higher average revenue than other robust policies while keeping a lower standard deviation. 
Competitive difference analysis of the one-way trading problem with limited information