The present perfect continuous and the present perfect

Compare the use of the present perfect continuous and the present perfect:

• The guests have been arriving since about 6 o'clock. ||| • Mark and Helena have arrived, they're in the sitting room.
• Since the operation two months ago, Joe has been learning to walk again. He can already take two or three steps unaided. ||| • I have learnt a lot about painting from Paul.
• She's been driving for 3 years now. |||  • We have driven all the way here without a break.

We use both the present perfect continuous and the present perfect to talk about something that started in the past and which affects the situation that exists now. The difference is that the present perfect continuous focuses on the activity or event which may or may not be finished. The present perfect, however, focuses on the effect of the activity or event, or the fact that something has been achieved.

Sometimes the difference between them is simply one of emphasis (see also Unit 10B):
• I've been following their discussions with great interest, (emphasises the activity; that is, my following their discussions)
• I've followed their discussions with great interest, (emphasises the result; I may now react to what was said or decided)
We can use either the present perfect continuous or the present perfect to talk about activities or events that are repeated again and again until now:
• Joseph has been kicking a football against the wall all afternoon, (or ...has kicked...)
• The press has been calling for her resignation for several weeks, (or ...has called...)
However, if we mention the number of times the activity or event was repeated, we use the present perfect rather than the present perfect continuous:
• I've bumped into Susan 3 times this week.
• He has played for the national team in 65 matches so far.
We use the present perfect rather than the present perfect continuous when we talk about longlasting or permanent situations, or when we want to emphasise that we are talking about the whole of a period of time until the present (see also Unit 5D):
• I have always admired Chester's work.
• They are the most delicious oranges I've ever eaten.
When we talk about more temporary situations we can often use either the present perfect continuous or the present perfect:
• 'Where's Dr Owen's office?' 'Sorry, I don't know. I've only worked / I've only been working
here for a couple of days.'
When we want to emphasise that a situation has changed over a period of time up to now, and may continue to change, we prefer the present perfect continuous to the present perfect:
• The pollution problem has been getting worse over the last decade.
• Sales have been increasing for some time.
However, if we talk about a specific change over a period of time which ends now, particularly to focus on the result of this change (see A), we use the present perfect:
• Prices have decreased by 7%. {= in a period up to now)
• The population has grown from 35 million in 1950 to 42 million today.