SAN JOSE — The 90-day moving average sales at North America-based semiconductor equipment manufacturers rose nearly 20% year-over-year to $1.63 billion in October.

Billings were up 9% over the revised September figure and 19.8% higher than the October 2015 level, according to SEMI.

Bookings fell 5.1% sequentially to $1.49 billion, while rising 12.2% over October, the trade group added.

The book-to-bill ratio plunged to 0.91, A book-to-bill of 0.91 means that $91 worth of orders were received for every $100 of product billed for the month.

It was the first time the ratio dropped below the benchmark 1.0 level since December 2015. A ratio below 1.0 suggests a contracting market.

Source: SEMI, November 2016. Billings and bookings figures are in millions of US dollars.