It is well known that there has been an increase in patent filings in many countries. But what can these patent filings tell us about the rate of technology change, as opposed to just the amount of patent activity?
One method of answering this is to look at the age of the backward citations. Patent examiners or applicants refer to patents in their search reports that they think are relevant to the patent being examined, and so we should be able to measure the rate of change based on how far back their citations go. We can measure this for either a single or group of patents in two different ways:
- By looking at the average age (difference in years between the patent and backward citations) of the backward citations
- By looking at the oldest backward citations, which tell us just how long patents thought to be relevent to the patent being examined have been around for.
From a statistical viewpoint, the second measure is flawed as just a single, potentially careless reference to a very old patent can distort the data. In fact we are mainly interested in the age of the majority of the citations - we may not need to know about the age of the very oldest citations to gain a reasonable idea of the rate of change. In practice, the age of the youngest 90% of the patent citations should give a reasonable idea of how long a particular technology has been around for (as only 10% of backward citations are older than this). We can call this measure 'Patent Turnover", being the maximum age of the youngest 90% of backwards citations.
We would also want to be a little selective about which backward citations we use to calculate these figures. As an example, imagine the development of a new drug diagnosis test with application for a wide variety of therapies, with patents filed for this new diagnosis. This development in turn may catalyse a number of new patents, including potentially in the area of Alzheimer's treatments (as just one example). The patent examiner or applicant reviewing this new Alzheimer's patent (that builds on this drug diagonsis invention) may quite rightly cite this drug diagnosis paten in their search report. But is the original drug diagnosis patent an Alzheimer's patent? We would argue not - it falls within another technology field, namely that of drug diagnosis, and so should be distinguished from any technology analysis of Alzheimer's patents.
Hence any analysis of the ages of the backward citations in any technology field should only consider the age of cited patents within the field itself - otherwise we are measuring the rate of change of other fields as well. Luckily, NPA lends itself very well to this type of analysis, as it is can be used to cluster patents with other patents within the same technology field, but to ignore patents cited outside of the nominated field.
Anyway, enough background - so what is the rate of change for a range of different technical fields? We have taken this data in Figure 1 from a variety of projects. The 'n' values for each type of technology refer to the number of relevant backward citations (to other patents in the same field) and not to the number of patents. These values are affected by the way each project was set up, and should not be interpreted in any other way than to confirm that there is sufficient data for the calculated values to statistically robust.
Figure 1 tells us:
- The average age of backward citations ranges from about 6.5 years (an ICT project and for Alzheimer's drugs) up to over 15 years for a mining industry project
- The "Patent Turnover" (age of youngest 90% of the patents) is around twice the average age of the citations.
- Within the area of smartphones, patent associated with mobile data access (to emails etc) had a lower citation age than patents associated with touchscreens. In simple terms, touchscreens appear to have been around for longer than mobile data access.
The varying Patent Turnover figures would suggest that companies may need to innovate at a faster rate within the ICT and pharmaceutical industries when compared to mechanical engineering and mining. Accordingly, a technology more than 10 years in the ICT industry may be obsolete, but technologies in the mechanical engineering and mining industries may be commercially relevant for much longer. These trends may not surprise many, but it is pleasing to see the patent data confirming what we probably all suspected.
We can also compare backward citation age gaps for different patent owners for a given technology, in this case for four leading owners in the mobile data access patent cluster in our previously published smartphone white paper, see Figure 2 (the number of backward citations used to calculate the Motorola values are less than ideal, and this may have affected this result).
So what do these owner results mean? There are different potential interpretations. We do know that Palm (remember the Palm Pilot?) and RIM (makers of Blackberry) were among the first companies to offer portable devices that could be used to read your email. It is possible that the examiners for the earlier patents filed by these companies could not find too many (then) recently filed prior art patents, and so had to go further back into the patent database to find relevent prior art. In contrast, later entrants to this market had more (then) recently filed patents to choose from. In this case, we could say that the early patents in this field were 'game changing' patents, Figure 3.
There is potentiallly a lot more that can be gleaned from this type of analysis, and we will continue to develop analysis tools to better interpret the wealth of data within the world's patent databases.
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