The assessment is based on a comprehensive and consistent body of evidence from multiple high-authority primary sources. The statement makes two claims: 1) the Nikkei index fell below the 51,000 level, and 2) this was concurrent with a decline in semiconductor stocks. Both claims are strongly supported.Multiple sources directly confirm that the Nikkei index fell below 51,000. For instance, one report gives a closing price of 50,376.53, another a close of 50,842.93, and others report intra-day drops to the 50,000 yen level or morning closes such as 50,434 yen. Another source explicitly states the index temporarily fell below 51,000 during a trading day. There is no contradictory evidence on this point.Crucially, the concurrency of this drop with a decline in semiconductor stocks is also explicitly and repeatedly confirmed. Several market reports directly attribute the Nikkei's significant drop to a sharp fall in 'semiconductor-related stocks' (半導体関連). One source specifically names the selling pressure on a major semiconductor company, Advantest, as a key factor. Other sources corroborate this by identifying the decline in 'high-tech stocks' (ハイテク株) as a 'burden' on the index as it fluctuated around the 51,000 level. Given that semiconductor stocks are a major component of the high-tech sector, these reports are mutually reinforcing.The sources are highly consistent, with no contradictions found. They collectively paint a clear picture of market behavior where weakness in the semiconductor sector directly drove the Nikkei index below the specified 51,000 threshold on multiple occasions.