Advanced concepts in Software Inc. naturally stem from the Market, how it works, what affects sales, etc. Being one of the most complex economic simulation games right now, there is a lot of stuff "under the hood" that really needs understanding, Market Overlap being one of them.
Since it semi regularly pops up in Discussions and Discord, here is the actual explanation of it.

Market Overlap is a Graph seen in Product's Details Window, when selecting the Competition. It shows the current Products released of that type, and under each, there is a Market Overlap value shown. What it represents is Market Interest in the products, and how similar are one to another.

Breaking into a market for a new company is hard, especially if there is an already established Competition. Likewise in Software Inc., there is a simulation period before the game starts, and when we arrive, there are products of all types, with even several sequels already published. Sequels mean more Market Recognition for the IP chain, more fans and more sales, but also tougher competition.

So, to be able to distinguish ourselves, we must either publish higher/est quality products, and slowly build our Reputation and fan base, or try to take risks, and do something new. Here in play comes the Market Overlap.

The base of all products in Software Inc. is the Technology, with Features. Initially in the Design document, we select Techs we want to use, and Features to implement, which increase the Market Interest for the Product. Logically, we want to hit 100% of current Market Interest, hoping for high sales, so the sliders should be set likewise. It's a no brainer.

Until now, I thought that Market Overlap is based on the Features implemented in the Product, and with different set of them, my products will have less Market Overlap with the Competition (less is better, in this case). But, I went more deep, tested some stuff, and realized that I was wrong from the beginning. Although Market Overlap must happen partially because of shared Technologies (Sys, 2d, Aud..), it is actually the Market Interest we set in Design Document, which is the key.

So let's look at the first example:
I created two PC OS-es, Zeus and Coin, with almost completely different set of Features, thinking I will end up will less Market Overlap, but it can out wrong:



As you can see, in the screenshot, Market Overlap for them is 97%, and that's because I used both time, during Document Design, the Auto Market Interest.

Now, here is the difference: I've created Sport 1 and Sport 2 games, semi-different features, but with big difference in Market Interest:

Sport 1



Sport 2



What was the final result ? Well Market Overlap of around 23%, which means, that these two products are not going to be direct competition:

Now that we understand what's influencing different Market Overlap, lets talk some more.
From my experience, Market Overlap is not the crucial part of the sales, it can help, but not in every case. For an example, there are products that can get 100% Market Interest since a Tech is missing early on (Adventure and RPG without 3D), however nobody else has it, so getting 100% of Market Interest different then the current need is totally fine, and those games will sell.

Other case includes, when there is low Competition, like for Sport games in my previous screenshots, there is no need to deviate from the Auto Market Interest, its better to go straight for it. Also, there is a player who publishes 3 tools for each of the techs, with every tool having filled one bar to the max. This is actually great, because he can publish 3 different Audio Tools at the same time, and not be in direct competition within themselves.

To conclude, Market Overlap should be important where the Competition is hard, and they have the upper hand with popular IPs, and also if you want to release several products of the same time, and not bankrupting because of the low sales.