ingresos pais en valor constante

Hola a todos,

I am working on a translation of a Spanish article about the impact of climate change on the tourism industry in Spain and the need for an appropriate response to the problem. During the translation process I've encountered a term which I am really lost about. I would therefore welcome your opinion. The term is

"ingresos pais en valor constante"

And the context is:

"El turismo espanol atraviesa un momento dificil que requiere una reconsideracion a fondo de las pautas de desarrollo vigentes en las ultimas decadas. Los rasgos criticos que apunptan a ese cambio se cifran en terminos de estancamiento de la economia turistica (pernoctaciones, gasto medio e ingresos pais en valor constante)....."

Here is my attempt:

"Spanish tourism is going through a difficult time that demands a thorough reconsideration of the development models that have been prevalent in the last decades. The critical features that point to this change are summed up in terms of the stagnation of tourism economy (overnight stays, average expenditure and ???????)"

I would very much welcome your opinion.

Muchas gracias!!!!

not positive but I think it's something like "national revenue in constant prices."