Making a big gift to draw other donors is only useful if the charity is highly effective.

The practice of donors offering to “match” gifts made to charities they support has become common in the charity world. In the run-up to Christmas, many offered to double donations. In the recent Challenge Campaign, for instance, money given to selected charities was doubled by the Big Give, set up by Sir Alec Reed, founder of Reed, the recruitment firm.

Others schemes propose different deals: one donor was offering to give $2 for every $1 given on Friday to Charity Navigator, a charity rating agency; while PayPal will add 1 percent to all donations made through its platform until New Year.

The UK’s Department for International Development does it too. Its UK Aid Match offered up to £5m from the UK aid budget to eight charities.

The theory is that the match attracts new donations. If your aim is helping your chosen charity to raise money, is it a good idea to offer to match other people’s contributions? The rigorous evidence suggests that it is.

Read more about the effectiveness of matching donations by Caroline Fiennes at Giving Evidence