Why 92%?

Yin Wood is 乙, a climbing vine; Yang Metal is 庚, an iron axe. 乙 and 庚 are one of the five traditional stem unions, so the pair starts at the top: 92. Unions are not adjusted for yin and yang.

Out of the 10 stems, 0 would score higher with Yin Wood.

Only the year's stem is used — this is a quick game, not a saju (Four Pillars) reading. The points are our own design; the five-element cycles are a tradition, not a science.