I'm currently doing some competitive analysis and market sizing. Its easy to get some basic figures for websites via Compete and Alexa, but I haven't found a good way to estimate the number of downloads iPhone/Android apps get.<p>Some apps tell you about how many downloads they have, but was wondering if there is a better way.<p>One way to guess would be based on the number of reviews (Assuming an average of.5% of users review an app, multiple # reviews by 200).<p>I'm sure you could nuance this by using other factors (e.g. maybe crappier apps or ones users have paid for have a higher % of users that review).<p>So, two questions:<p>(1) Anyone have any data on the % of users that review an app (the app rating would be a useful data point),<p>and<p>(2) Know any better ways to estimate the number of app downloads?