I currently run a two person web development team. My partner and I offer Ruby on Rails programming for our clients (small companies). We typically charge $75/hr for most of our clients but we have two old clients for which we charge $50/hr and $55/hr respectively from when we first started. The former we have never had a rate increase since we started with them in early 2007 and the later we have not had a rate increase in two years. We bill about 50-80 hours a month of work per client for both clients. Both clients are excellent to deal with and I want to continue our strong relationship going forward.
I would like to get both these clients rates up to $75/hr which I feel is more in line with market value and our level of expertise. What is the best way to communicate this? Should I do it in person? Is an email ok? Also, I'm not sure asking a client to go from $50/hr to $75/hr is acceptable since that is a 50% jump. What is an appropriate rate increase per year in software professional services? Any thoughts will be greatly apprecited!