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.
| 
 Billings  | 
 Bookings  | 
 Book-to-Bill  | 
|
| 
 May 2016  | 
 $1,601.5  | 
 $1,750.5  | 
 1.09  | 
| 
 June 2016  | 
 $1,715.2  | 
 $1,714.3  | 
 1.00  | 
| 
 July 2016  | 
 $1,707.9  | 
 $1,795.4  | 
 1.05  | 
| 
 August 2016  | 
 $1,709.0  | 
 $1,753.4  | 
 1.03  | 
| 
 September 2016 (final)  | 
 $1,493.3  | 
 $1,567.2  | 
 1.05  | 
| 
 October 2016 (prelim)  | 
 $1,627.5  | 
 $1,487.2  | 
 0.91  | 
Source: SEMI, November 2016. Billings and bookings figures are in millions of US dollars.