Budgets are tight these days, so if you’re launching a product on a global scale you’ll likely have to scale-back on your launch spending. Ideally you’d conduct market research in 3+ markets to make sure you get feedback from a good range of customers, but, if you pick the right markets, you can get by with conducting research in only two markets.
Pick two markets that represent different ends of the spectrum from a market dynamics perspective. For example, I’ve been engaged by a client that has a great product pipeline in the consumer healthcare space and wants to understand how to best position each product in the portfolio. The plan is to conduct research in the US (their largest market) and in one of their emerging markets (in this case China). This will give them an established market and an emerging market perspective, from which they’ll be able to extrapolate likely scenarios for markets within that spectrum. Now, this isn’t perfect, but it should get you 80% there.