Growth in this context is that there are a larger volume of videos each year. So each year a single video is exponentially a smaller and smaller percentage of the total.
For example, if in year N youtube has f(N) new video. Let assume f(N) = cN^2. It's a crazy rate of growth. It's far better than the real world Youtube, which grew rather linearly.
But the rate of "videos that are older than 5 years" is still faster than that, because it would be cubic instead of quadratic. Unless the it's really exponential (it isn't), "videos that are older than 5 years" will always surpass "new videos this year" eventually.
Video sensors are continuously getting cheaper, better and more more prevalent over time. The trend is towards capturing all angles of everything, everywhere, at increasingly higher resolutions.
