  We study four promotions offered on Apple's mobile app store that vary in
user exposure, price discount and redemption procedure. We find that promotions
that are full-price discounted and digital (i.e., the redemption procedure is a
few taps on the smartphone) are the ones that cause the largest increase in
downloads. Investigating the effect on ratings, we find neutral or positive
effects on the ratings for all full-price discounted promotions but negative
short-term effects on the ratings of apps promoted by substantial, but only
partial, price discounts. Furthermore, we find that high barrier promotions
induce a rich-get-richer effects, with apps that were popular before the
promotion receiving, generally, larger benefits. In contrast, low barrier
promotions cause, on average, the same increase in sales for all participating
apps regardless their characteristics or their previous popularity. Finally, we
explore the effect of these promotions on the competition of the featured apps
and find negative externalities when the promotion is low barrier and positive
when it's high barrier.
