For a finite binary word w and x∈{0,1}, let rw(x) be the largest integer r≥1 for which wx ends in ur for some nonempty word u, and let ℓw(x) be the largest length ∣u∣ among witnesses for that maximal r. Define b1=0; for m≥2, let bm be the bit x that minimizes (rb1⋯bm−1(x),ℓb1⋯bm−1(x)) in lexicographic order. Does the limit limN→∞N−1∣{1≤m≤N:bm=0}∣ exist and equal 1/2?