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which is due for renewal and which is equal to the 
investment 20 years earlier. The excess is the greater, 
the greater the accumulation, it will therefore be 
largest in the later stages of the "long boom", and will 
represent a damping influence (just to keep up a given 
capacity you will have to invest less than the depreciation 
quota). At the later stages of a "long recession" this 
excess depreciation will be much less (or zero, if there 
has been stagnation). 
Speaking in terms of "long waves" and placing so much 
weight on the active role of the rate of growth of capital, 
we may well ask how the process is hemmed in - bounded - 
within what are after all fairly narrow limits. 
In the upward direction the limits are given by resources: 
They make themselves felt as bottlenecks. Basically the 
speed of development is limited by the capacity of people 
and of a society to learn. The impression is that at 
certain times and places we are not so very far away from 
this limit. It is much more difficult to answer the 
question - which is perhaps topical - where the lower limit 
lies, and what forces may reactivate a sluggish secular 
movement. In analogy to the trade cycle, we may say that 
removal of the excess capacity will be a condition. It is 
rather hard to imagine at the moment that this will easily