Sampling bias

If Ecclesiastes was written by Solomon (or perhaps in his honor?) then it may be simple to understand the curious passage in which he says he's found 1 man in a thousand but not a single woman (in context he's looking for the upright and wise).

If, as 1 Kings 11 suggests, his wives were political acquisitions, you'd expect the bulk of them to be "ambassadors for their families/countries," and always keeping their eyes on what influence they can have. I don't think many kings pick their concubines for qualities like wisdom. Together these groups don't sound like a pool one could draw from to find uprightness and wisdom. In that culture, they'd represent most of the women he met.

In other words, it was his own fault his search failed.