The Patent Prosecution Highway (PPH) program accelerates examination among participating patent offices. The PPH program first began as a trial program between the U.S. Patent and Trademark Office (USPTO) and the Japan Patent Office (JPO) in 2006, to avoid duplicate work efforts and expedite patentability decisions between patent offices.  Since then, the program has grown to include over 40 patent offices, including the European Patent Office (EPO), Korean Intellectual Property Office (KIPO), China National Intellectual Property Administration (CNIPA), and Canadian Intellectual Property Office (CIPO). This article discusses a brief overview of the PPH program and surveys PPH activity in participating patent offices.
Under the PPH program, when an applicant receives a final ruling that an application with at least one claim is determined to be patentable at a first patent office (“office of earlier examination”), the applicant can request accelerated examination of corresponding claims in a corresponding application pending in a second patent office (“office of later examination”). As compared to standard examination, the office of later examination can leverage search results and analysis performed by the office of earlier examination, thus resulting in a speedier final disposition (e.g., issuance of a Notice of Allowance) of the application at the second patent office.
In addition to receiving the final ruling indicating that at least one claim is patentable, the PPH program has other requirements. A notable requirement is the submission of claims to the office of later examination that sufficiently correspond to those found allowable by the office of earlier examination. Another notable requirement is that examination of the subject patent application by the office of later examination must not have begun. 
Survey of PPH Activity in Participating Patent Offices
Table 1 shows the top five patent offices of earlier examination under the PPH program through June 2018.  The JPO has received the most PPH requests—as the office of earlier examination—at approximately 70,000 requests, followed by the USPTO at approximately 55,000 requests. The EPO, KIPO, and CNIPA each received less than half of the requests received by the JPO and USPTO at approximately 20,000, 15,000, and 5,000 requests, respectively.
Table 2 shows the top five patent offices of later examination.  The USPTO received the most PPH requests—as the office of later examination—at over 50,000 requests through June 2018. As the office of later examination, the number of PPH requests received by the USPTO nearly doubles (or even triples) the number of requests received by each of the CNIPA (approximately 27,000 requests), JPO (approximately 25,000 requests), KIPO (approximately 20,000 requests), and CIPA (approximately 15,000 requests).
Table 3 shows the top 10 PPH filing countries and office of earlier examination/office of later examination combination.  The JPO/USPTO combination received the most PPH requests—with the JPO being the office of earlier examination and the USPTO being the office of later examination—receiving over 20,000 PPH requests. This number of PPH requests is over 5,000 more requests received by each of the JPO/CNIPA (approximately 12,000 requests), USPTO/CIPA (approximately 11,000 requests), and EPO/USPTO (approximately 10,000 requests) combinations. The USPTO/CNIPA, KIPO/USPTO, JPO/KIPO, and USPTO/KIPO combinations received approximately between 7,000 and 9,000 PPH requests. The JPO/EPO combination received approximately 5,000 PPH requests.
The above discussion indicates that the patent offices with the most PPH activity are the JPO and USPTO, with the JPO being the office of earlier examination receiving the most PPH requests and the USPTO being the office of later examination receiving the most PPH requests. The EPO, KIPO, CNIPA, and CIPA also receive a significant number of PPH requests. Thus, for applicants seeking patent protection in these jurisdictions, the PPH program may be a viable vehicle to obtain patents faster than by standard examination.
 PPH data from June 2018— http://www.jpo.go.jp/e/toppage/pph-portal/statistics.html