It's been said time and time again on this site: You can't time the market, you just can't. I understand the logic behind this, but lately I've been thinking about a somewhat related scenario and I would love to hear your thoughts on this.
While you may never be able to know when the markets are at their heights or lows, couldn't you leverage the fact that fluctuations will no doubt occur? The bible (I'm not religious, but still) informs us that the cycle of economical up- and downturns is old, very old, and other sources seem to agree with this notion. I myself am in my mid forties and I've seen several in my lifetime, they seem to occur on the order of magnitude of decades. It seems that the saying "after rain comes sunshine" applies here. Always, as far as I can tell.
So consider the following very simple investment strategy, executed by someone young enough to see it through:
Whenever there is an economic downturn (as evidenced simply by a majority of economists saying: "hey, we're in a downturn") you invest your money into a diversified portfolio that closely resembles the economy as a whole. Now you wait until there is a upswing (as evidenced simply by a majority of economists saying: "hey, we're in a upswing") and you cash it all out. Rinse and repeat.
Would such a strategy be viable?
Edit: I'm not asking about maximizing profits here, in fact quite the opposite, I'm wondering if this would be viable as a low risk, low reward kind of strategy.
Edit 2: I'm very much aware nobody knows when the economy will be at it's peak, or when it's at its lowest. However, last year I was very much aware we were on an upswing, just like in 2008 I was very much aware we were in a downturn. In this context, that knowledge would be enough. (Or if it isn't, please enlighten me but again, I don't care about missed opportunity or maximum profits here).
Edit 3: As I commented on @BobBearker's answer, which somewhat but not entirely addresses my thoughts: I always understood "timing the market" to mean "knowing when it peaks or bottoms out", which wouldn't be required for this to work, neither would (I think, not sure) knowing the high point or low point. So let's say buy at -15%, sell at +15%, to make it a little less vague (edit: this was terribly distracting, should have kept it vague). And when you miss your opportunity because of a sharp reversal you simply wait for the next time. I guess what I'm asking is: Could you leverage the fluctuations by themselves, without knowing anything else but: "what goes up must come down and vice versa".
P.S. I've used the words "upswing" and "downturn" because I was looking for a proper translation for the dutch words "hoog- en laagconjuctuur" but couldn't find them. Boom/bust as I understand it seems to relate to the excesses, not the "normal" fluctuations, but feel free to edit or suggest words that would better convey that meaning.