The New Scientist has a news item on Entering a dark age of innovation, reporting on the research of Jonathan Huebner, a physicist who claims that "the rate of technological innovation reached a peak a century ago and has been declining ever since." His main finding is that the per-capita innovation of humanity has been in decline, it is currently at ~1600AD levels and will soon (by 2024) plummet to medieval levels.
Dr. Huebner proposes that technological innovation is limited both physically (e.g., it is impossible to transcend the limitations of natural laws), but also economically (it may be possible, but not practical to do something). According to his interpretation, the observed trend due to economic limitations, although he does leave open the possibility that it may be cognitive, i.e., that the human mind may have been pushed close to its limit.
Technological Forecasting and Social Change (Article in Press)
A possible declining trend for worldwide innovation
A comparison is made between a model of technology in which the level of technology advances exponentially without limit and a model with an economic limit. The model with an economic limit best fits data obtained from lists of events in the history of science and technology as well as the patent history in the United States. The rate of innovation peaked in the year 1873 and is now rapidly declining. We are at an estimated 85% of the economic limit of technology, and it is projected that we will reach 90% in 2018 and 95% in 2038.